Liquid-crystal display

ABSTRACT

In a liquid-crystal display ( 10 ), unpolarized light from a light source ( 12 ) passes through a linear polarization separation layer ( 14 ) and strikes a liquid-crystal cell ( 16 ). The liquid-crystal cell ( 16 ), in response to an applied electrical field, changes the direction of a director, so as to change the direction of the electrical field oscillation vector of the incident linearly polarized light by substantially 0 to 90°, this light then striking a dichroic linear polarization layer ( 18 ) on the surface, whereby only a component coincident with the polarization transmission axis thereof is allowed to exit to the outside. The dichroic linear polarization layer ( 18 ) transmits 50% of this incident light, and absorbs the remaining 50%.

TECHNICAL FIELD

The present invention relates to a liquid-crystal display having adichroic polarizing layer that passes a light component of onepolarization and absorbs a light component of another polarization, apolarization separation layer that passes a light component of onepolarization and reflects a light component of another polarization, anda liquid-crystal cell, the retardation value or liquid crystal directorsof which change in response to an electrical field.

BACKGROUND ART

A liquid-crystal display modulates polarized light obtained by passingthe light through a polarizer and, as shown in FIG. 31, in a typicalliquid-crystal display 1 of the past, light exiting from a light source2 is caused to strike a light-absorbing type of dichroic linearpolarizer 3, the linearly polarized light obtained there from being madeto strike a liquid-crystal cell 4.

In the liquid-crystal display 1, light that strikes the liquid-crystalcell 4 and passes therethrough as polarized light, is modulated by theaction of a voltage applied to electrodes provided on the liquid-crystalcell 4, which generates an electrical field that changes the liquidcrystal within the cell is changed, or exits from the liquid-crystalcell 4 unchanged if there is no electrical field, after which, by theaction of an absorption type dichroic linear polarizer disposed outsidethe liquid-crystal cell 4, light of only a specific polarizationdirection is transmitted.

The absorption type dichroic linear polarizers 3 and 5 pass polarizedlight of a transmission axis direction, and absorb almost all light of adirection perpendicular to the transmission axis direction. Therefore,approximately 50% of the light (unpolarized light) exiting from theliquid-crystal display 2 is absorbed by the dichroic linear polarizer 3,so that there is an overall decrease in the efficiency of light usage inthe liquid-crystal display 1, and to achieve a sufficient intensity atthe liquid-crystal display screen, it becomes necessary to cause a largeamount of light from the light source to strike the dichroic linearpolarizer 3.

However, if the amount of exiting light from the light source 2increases in this manner, there is not only an increase in electricalpower consumption, but also an increase in the heat generated by thelight source 2, thus leading to the problem of an adverse affect on theliquid-crystal cell 4.

In contrast to the above, as disclosed in PC (WO) 4-502524 and theJapanese Unexamined Patent Application publication 6-130424, there hasbeen a proposal of a liquid-crystal display in which, non-polarizedlight from a light source is separated into right-rotational orleft-rotational circularly polarized light, by means of transmission orreflection using a cholesteric liquid-crystal layer, circularlypolarized transmitted light of one rotational direction being caused tostrike a liquid-crystal cell, and circularly polarized reflected lightof another rotational direction being reflected, so as to reverse itsrotational direction and cause it to pass through a cholestericliquid-crystal layer, thereby improving the efficiency of light usage.

As disclosed in PC (WO) 9-506985, there has been a proposal of aliquid-crystal display in which non-polarized light from a light sourceis separated into two linearly polarized lights by transmission orreflection using an extended multilayer film, one transmitted linearlypolarized light being caused to strike a liquid-crystal cell, and theother, reflected linearly polarized light having a direction that isperpendicular to the aforementioned light having its polarizationdirection changed, and being guided back to the extended multilayerfilm, thereby improving the efficiency of light usage.

In the liquid-crystal displays disclosed in the PC (WO) 4-502524 and theJapanese Unexamined Patent Application publication 6-130424, when noelectrical field is applied to it, liquid-crystal layer shifts the phaseof light an amount of either π (λ/2) or π/2 (λ/4), and when anelectrical field is applied the liquid-crystal layer does not shift thephase of the light, light exiting from this liquid-crystal layerstriking a circular polarizer disposed outside, it being transmitted orreflected, in accordance with its degree of polarization.

In the liquid-crystal display disclosed in PC (WO) 9-506985, linearlypolarized light of one direction that has passed through an extendedmultilayer film is caused to strike a liquid-crystal cell, althoughthere is no disclosure with regard to the retardation of theliquid-crystal layer.

In the liquid-crystal displays disclosed in PC (WO) 4-502524 andJapanese Unexamined Patent Application publication 6-130424, for thefollowing reason, there is an extreme worsening of readability in theliquid-crystal display, and a great loss of contrast, making the displayquality insufficient.

Specifically, in the liquid-crystal display of PC (WO) 4-502524, becausea circular polarizer disposed outside of the liquid-crystal layer anddirectly visible is made from a low pitch cholesteric applied filmhaving spectrally selective reflectivity, approximately 50% of theexternal light striking this circular polarizer is reflected, so thatthis directly entering the eyes of an observer, thereby causing a severeworsening of readability.

In the same manner, in the liquid-crystal display of Japanese UnexaminedPatent Application publication 6-130424, the color-selective layer thatis directly observable from the outside is a circular polarizer made ofa cholesteric liquid crystal, and this, similar to the case cited above,directly reflects approximately 50% of the incident external light,thereby greatly reducing the readability of the display.

DISCLOSURE OF INVENTION

Accordingly, the present invention was made with the above-describedproblems of the past in mind, and has as an object to provide aliquid-crystal display having a simple configuration, which has no lossof readability or great decrease in contrast caused by external light,and in particular in the case of a transmissive type liquid-crystaldisplay, can provide a great improvement in the efficiency of lightusage, and in the case of a reflective type liquid-crystal display canprovide both high contrast and color display, making use of thebirefringence in the liquid crystal.

A first aspect of the present invention is to provide a liquid-crystaldisplay, as described in claim 1, comprising a dichroic polarizing layerhaving one of a function whereby of the incident light, a lightcomponent having circular polarization of one direction, either right orleft, is transmitted, and a component of the other circularlypolarization direction is reflected, and a function whereby one linearlypolarized light component is transmitted and a linearly polarized lightcomponent perpendicular thereto is absorbed, a liquid-crystal cellincluding a liquid-crystal layer that shifts the phase of light passingtherethrough and electrodes for applying an electrical field to theliquid-crystal layer, whereby one of circularly polarized light andlinearly polarized light incident after being transmitted through thedichroic polarizing layer is converted to the other before it exits theother side or is not converted but the liquid-crystal cell also has onefunction of a function that changes the ellipticity of the light ifexiting as circularly polarized light or changes the direction ofpolarization of the light it if it is exiting as linearly polarizedlight, and a polarization separation layer having one of a function oftransmitting a light component having circular polarization of onedirection, either right or left, and reflecting a component of the othercircular polarization direction, and a function of transmitting onelinearly polarized light component and reflecting another componenthaving a polarization direction perpendicular thereto, these beingdisposed in this sequence as seen from the observation side, whereinlight is caused to be incident from either the dichroic polarizing layeror the polarization separation layer side.

In the above-noted liquid-crystal display, the dichroic polarizing layercan be a dichroic circular polarizing layer which, of incident lighttransmits a circularly polarized light component of one direction,either right or left, and absorbs a circularly polarized light componentof the other direction, said liquid-crystal layer having a retardationvalue that causes a phase shift in the transmitted light that issubstantially n/2, the liquid-crystal cell converting the incidentcircularly polarized light to linearly polarized light before it exitsfrom the opposite side by applying an electrical field from saidelectrodes to the liquid-crystal layer so as to change the orientationof the directors thereof, thereby causing a change in the polarizationaxis of the linearly polarized light, the polarization separation layerbeing made a linear polarization separation layer that, of the incidentlight thereto, transmits a light component of one linear polarizationand reflects another linearly polarized light component havingpolarization perpendicular thereto.

In the above-noted liquid-crystal display, a circuit can be provided forcontrol of a voltage between the electrodes, so that the direction ofthe directors of the liquid crystal in the liquid-crystal cell ischanged by substantially −45 to +45 degrees with respect to theelectrical vector direction of the incident linearly polarized light.

In the above-noted liquid-crystal display, the dichroic polarizing layercan be a dichroic circular polarizing layer which, of incident lighttransmits a circularly polarized light component of one direction,either right or left, and absorbs a circularly polarized light componentof the other direction the liquid-crystal cell having the effect ofshifting the circularly polarized light phase of incident lightsubstantially by 0 to π, when said electrical field is applied to saidliquid-crystal layer from the electrodes so as to change the retardationvalue thereof, the polarization separation layer being made a circularpolarization separation layer that, of the incident light thereto,transmits a light component of one circular polarization, either rightor left, and reflects another circularly polarized light componenthaving the opposite polarization.

In the above-noted liquid-crystal display, the dichroic polarizing layercan be made a dichroic circular polarizing layer which, of incidentlight transmits one circularly polarized light component and absorbsanother circularly polarized light component, said liquid-crystal cellhaving the effect of shifting a linealy polarized light phase ofincident light substantially by −π/2 to π/2, when said electrical fieldis applied to said liquid-crystal layer from said electrodes so as tochange the retardation value thereof, and the polarization separationlayer being a linear polarization separation layer that, of the incidentlight thereto, transmits a light component of one linear polarizationand reflects another linearly polarized light component havingpolarization perpendicular thereto.

In the above-noted liquid-crystal display, the dichroic polarizing layercan be a dichroic linear polarizing layer which, of incident lighttransmits one linearly polarized light component and absorbs a linearlypolarized light component perpendicular thereto, the liquid-crystallayer having a retardation value that causes a phase shift intransmitted light of substantially π/2, the liquid-crystal cellconverting incident linearly polarized light to circularly polarizedlight before it exits from the opposite side, the director direction ofthe liquid crystal being changed by applying the electrical field to theliquid crystal from the electrodes, thereby changing the ellipticity ofthe circularly polarized light, and the polarization separation layerbeing made a circular polarization separation layer that, of theincident light thereto, transmits a light component of one circularpolarization, either right or left, and reflects another circularlypolarized light component having the opposite polarization.

In the above-noted liquid-crystal display, a circuit can be provided forcontrol of a voltage between the electrodes, so that the direction ofthe directors of the liquid crystal in the liquid-crystal cell ischanged by substantially −45 to +45 degrees with respect to the lighttransmission axis of the dichroic linear polarizing layer.

In the above-noted liquid-crystal display, the dichroic polarizing layercan be a dichroic linear polarizing layer which, of incident lighttransmits one linearly polarized light component and absorbs a linearlypolarized light component perpendicular thereto, the liquid-crystal cellbeing such that, with the electrical field applied to the liquid-crystallayer from the electrodes, the retardation value of the liquid crystalis change so as to shift the phase of the incident linearly polarizedlight substantially from 0 to π, and the polarization separation layerbeing a linear polarization separation layer that, of the incident lightthereto, transmits a light component of one linear polarization andreflects another linearly polarized light component having polarizationperpendicular thereto.

In the above-noted liquid-crystal display, the dichroic polarizing layercan be a dichroic linear polarizing layer which, of incident lighttransmits one linearly polarized light component and absorbs a linearlypolarized light component perpendicular thereto, the liquid-crystal cellbeing such that, with the electrical field applied to the liquid-crystallayer from the electrodes, the retardation value of the liquid crystalis changed so as to shift the phase of the incident light substantially−π/2 to +π/2, and the polarization separation layer being a circularpolarization separation layer transmitting one circularly polarizedlight component of the incident light and reflecting the othercircularly polarized light component of the incident light.

In the above-noted liquid-crystal display, the liquid-crystal cell isheld between two substrates the electrodes being disposed on the twosubstrates, with the liquid crystal therebetween. When voltage isapplied to the electrodes, the mode is enabled in which angle of theliquid crystal molecules with respect to the substrate surfaces changes,thereby changing the retardation value of the liquid crystal.

In the above-noted liquid-crystal display, the dichroic polarizing layercan be a dichroic linear polarizing layer which, of incident lighttransmits one linearly polarized light component and absorbs a linearlypolarized light component perpendicular thereto, the liquid-crystal cellincluding a liquid-crystal layer having a retardation value that shiftsthe phase of transmitted light substantially π, and applying theelectrical field to the liquid-crystal layer from the electrodes so asto change the orientation of the directors thereof, thereby causing achange in the polarization axis of the linearly polarized light to theopposite direction which perpendicular to the original light, and thepolarization separation layer being made a linear polarizationseparation layer that, of the linearly polarized light incident thereto,transmits a light component of one linear polarization and reflectsanother linearly polarized light component having polarizationperpendicular thereto.

In the above-noted liquid-crystal display, a circuit can be provided forcontrol of a voltage between the electrodes, so that the direction ofthe directors of the liquid crystal in the liquid-crystal cell ischanged by substantially 0 to +45 degrees.

In the above-noted liquid-crystal display, the liquid-crystal layer ofthe liquid-crystal cell can be held between two substrates, theelectrodes being formed on one substrate, wherein when a voltage isapplied to the electrode, the resulting electrical field as a part thatis substantially parallel to the substrate surface, the direction of themost of the liquid crystal molecules within the liquid-crystal layerbeing in a mode in which they remain substantially parallel to thesubstrate surface.

In the above-noted liquid-crystal display, the circular polarizationseparation layer can be made of a rotation-selective layer made of acholesteric liquid crystal.

In the above-noted liquid-crystal display, the circular polarizationseparation layer can be made of a laminate of a phase-shifting layerhaving a retardation value that shifts the phase of a transmitted lightby substantially π/2 and three or more films having birefringence, thisbeing a planar multilayer structure wherein of two lights havingoscillation directions mutual perpendicular within the plane of eachlayer, the difference in index of refraction between layers adjacent inthe thickness direction with respect to one light is different from thedifference in the index of refraction between adjacent layers in thethickness direction for the other light, linearly polarized lighttransmitted through or reflected by this planar multilayer structurebeing converted to circularly polarized light.

In the above-noted liquid-crystal display, the linear polarizationseparation layer can be a planar multilayer structure of three or morefilms having birefringence, wherein of two lights having oscillationdirections mutually perpendicular within the plane of each layer, thedifference in index of refraction between layers adjacent in thethickness direction with respect to one light is different from thedifference in index of refraction between layers adjacent in thethickness direction with respect to the other light.

In the above-noted liquid-crystal display, the linear polarizationseparation layer can be made up of a phase-shifting layer having aretardation value that shifts the phase of transmitted light bysubstantially π/2, and a rotation-selective layer made of a cholestericliquid-crystal layer, wherein circularly polarized light transmittedthrough or reflected by the cholesteric layer is converted to linearlypolarized light.

In the above-noted liquid-crystal display, an auxiliary dichroic linearpolarizing layer can be provided between the liquid-crystal cell and thelinear polarization separation layer, whereby, of the incident light,one linearly polarized light component is transmitted, and anotherlinearly polarized light component perpendicular thereto is absorbed.

In the above-noted liquid-crystal display, an auxiliary dichroiccircular polarizing layer can be provided between the liquid-crystalcell and the circular polarization separation layer, whereby, of theincident light, one circularly polarized light component of either rightor left rotation is transmitted, and another circularly polarized lightcomponent of the opposite direction is absorbed.

In the above-noted liquid-crystal display, a light source can bedisposed on the side of the polarization separation layer opposite fromthe liquid-crystal cell, light from the light source passing through thepolarization separation layer and striking the liquid-crystal cell.

In the above-noted liquid-crystal display, a light-absorbing layer canbe disposed on the side of the polarization separation layer oppositefrom the liquid-crystal cell, whereby light having passed through thepolarization separation layer is absorbed.

In the present invention, in addition to using a light-absorbingdichroic polarizer on the externally viewable surface, the retardationvalue or liquid crystal director is selected, in accordance with thisdichroic polarizer, thereby eliminating a reduction in light utilizationefficiency and preventing a loss of display contrast and worsening ofreadability caused by external light, while using birefringence of theliquid-crystal layer to achieve a color liquid-crystal display with goodcontrast.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a simplified cross-section view showing an exploded view of aliquid-crystal display according to a first embodiment of the presentinvention.

FIG. 2 is a graph of a Poincare sphere illustrating various polarizationrelationships.

FIG. 3 is a graph showing the symbols used to describe ellipticallypolarized light and a cross-section of elliptically polarized light.

FIG. 4 is a cross-section view showing an enlarge view of aliquid-crystal cell in the above-noted liquid-crystal display.

FIG. 5 is an enlarged cross-section view showing the director directionsof a liquid crystal in the above-noted liquid-crystal cell.

FIG. 6 is an enlarged cross-section view showing the director directionsof a liquid crystal in the above-noted liquid-crystal cell when anelectrical field is applied.

FIG. 7 is a cross-section view similar to FIG. 1, showing the darkcondition of a display function of the above-noted liquid-crystaldisplay.

FIG. 8 is a simplified cross-section view showing an exploded view ofthe main part of a liquid-crystal display according to a secondembodiment of the present invention.

FIG. 9 is a cross-section view similar to FIG. 7, showing the darkcondition of a display of the above-noted liquid-crystal display.

FIG. 10 is a simplified cross-section view showing an exploded view ofthe main part of a liquid-crystal display according to a thirdembodiment of the present invention.

FIG. 11 is a cross-section view similar to FIG. 10, showing thecondition of a dark display of the above-noted liquid-crystal display.

FIG. 12 is a cross-section view similar to FIG. 6, showing aliquid-crystal display according to a fourth embodiment of the presentinvention.

FIG. 13 is a cross-section view similar to FIG. 12, showing thecondition of a dark display of the above-noted liquid-crystal display.

FIG. 14 is a simplified cross-section view showing an exploded view ofthe main part of a liquid-crystal display according to a fifthembodiment of the present invention.

FIG. 15 is an enlarged cross-section view of a liquid-crystal cell inthe above-noted liquid-crystal display.

FIG. 16 is a simplified cross-section view showing the condition of adark display in the above-noted liquid-crystal display.

FIG. 17 is a simplified cross-section view showing an exploded view ofthe main part of a liquid-crystal display according to a sixthembodiment of the present invention.

FIG. 18 is a simplified cross-section view showing the condition of adark display in the above-noted liquid-crystal display.

FIG. 19 is a cross-section view similar to FIG. 14, showing aliquid-crystal display according to a seventh embodiment of the presentinvention.

FIG. 20 is a cross-section view similar to FIG. 14, showing aliquid-crystal display according to a eight embodiment of the presentinvention.

FIG. 21 is a simplified cross-section view showing an exploded view ofthe main part of a liquid-crystal display according to a ninthembodiment of the present invention.

FIG. 22 is an enlarged cross-section view of a liquid-crystal cell inthe above-noted liquid-crystal display.

FIG. 23 is a simplified cross-section view showing the condition of adark display in the liquid-crystal display of FIG. 21.

FIG. 24 is a simplified cross-section view showing an exploded view ofthe main part of a liquid-crystal display according to a tenthembodiment of the present invention.

FIG. 25 is a cross-section view similar to FIG. 24, showing thecondition of a dark display in the above-noted liquid-crystal display.

FIG. 26 is a simplified cross-section view showing an exploded view ofthe main parts of a liquid-crystal display according to an eleventhembodiment of the present invention.

FIG. 27 is a simplified cross-section view showing an exploded view ofthe main parts of a liquid-crystal display according to the firstembodiment of the present invention.

FIG. 28 is an enlarged cross-section view of a liquid-crystal cell inthe above-noted liquid-crystal display.

FIG. 29 is a cross-section view similar to FIG. 27, showing the darkdisplay function of the above-noted liquid-crystal display.

FIG. 30 is a simplified cross-section view showing an exploded view ofthe main part of a liquid-crystal display according to a thirteenthembodiment of the present invention.

FIG. 31 is a cross-section view similar to FIG. 1, showing aliquid-crystal display of the past.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention are described in detailbelow, with references being made to relevant accompanying drawings.

As shown in FIG. 1, a liquid-crystal display 10 according to the firstembodiment of the present invention includes a light source 12 thatemits non-polarized light, a circular polarization separation layer 14,which, of light emitted form the light source, transmits one(elliptical) circularly polarized light, a liquid-crystal cell 16, alight-absorption type dichroic linear polarizing layer 18 disposed onthe side of the liquid-crystal cell 16 opposite from the circularpolarization separation layer 14, which receives linearly polarizedlight transmitted through the liquid-crystal cell 16, pixel electrodes24A and 24B, which apply an electrical field to the liquid-crystal layer22, wherein circularly polarized light passing through an auxiliarydichroic circular polarizing layer 13 is converted to linearly polarizedlight before it exits from the opposite direction from the circularpolarization separation layer 14, this linearly polarized light passingthrough the liquid-crystal cell 16 being received by thelight-absorption type dichroic linear polarizing layer 18 and furtherwherein an electrical field is applied to the liquid-crystal layer 22from the pixel electrodes 24A and 24B, thereby changing the direction ofthe directors of the liquid crystal, which changes the polarization axisof the linearly polarized light.

In FIG. 1, the symbols “

” and “•” indicate electrical field oscillation vectors of linearlypolarized light, “

” being directions within the plane of the drawing and “•” being adirection perpendicular to the plane of the drawing.

A reflective layer 12A is formed on the rear surface (lower surface asshown in FIG. 1) of the light source 12. The reflective layer 12Areflects light that has exited the light source 12 and been reflected tothe circular polarization separation layer 14 back in the direction ofthe circular polarization separation layer 14, whereupon the phase ofthe circularly polarized light component is reversed, or the light ismade non-polarized light, so that it can pass through the circularpolarization separation layer 14.

The circular polarization separation layer 14 is made of, for example acholesteric liquid-crystal layer, and the light-absorption type dichroiclinear polarizing layer 18 passes polarized light of the transmissionaxis direction and absorbs almost all polarized light of a directionperpendicular to the transmission axis, this being formed either byimmersing a PVA (polyvinyl alcohol) film in an aqueous solution ofpotassium iodide, and then extending the PVA film in one direction in aboric acid solution, so as to laminate a protective film in which iodineatoms absorbed by the PVA film are oriented in one direction, an aso-called iodine-based polarizer, or by a dye-based dichroic polarizer,or the like.

The liquid crystal in the liquid-crystal layer 16 is adjusted so thatits retardation value causes a shift of substantially π/2 in the phaseof transmitted light, regardless of whether an electrical field isapplied.

The adjustment can be done by a known liquid crystal (for example, anematic liquid crystal) by control of the birefringence and thickness ofthe liquid-crystal layer.

The Poincare sphere shown in FIG. 2 is used in describing polarization,and in investigating how the form of the polarization changes when thephase is changed. In FIG. 2, the poles at the top and bottom of thesphere represent left and right circular polarizations, respectively,and a point on the equator represents linear polarization, with otherpoints representing elliptically polarized light.

An arbitrary point H on the equator represents horizontal polarization,and a point V on other end of a diameter that passes through the point Hrepresents vertical polarization. The diameter of the sphere isgenerally taken to be 1, and can alternately be proportional to theintensity of light.

An arbitrary point P on the surface of a unit radius Poincare sphere isrepresented by a longitude 2% and a latitude 2ω, in which case λ and ωsatisfy the conditions −180°<2λ<180° and −90°<2ω<90°, respectively.

The longitude is taken as being positive when measured in the clockwisedirection from point H, and the latitude is taken as being positive whenmeasured upward from the equator, that is, toward the pole representingright circular polarization. The coordinates of the point P in FIG. 2,therefore, are positive.

The arbitrary point P represents total elliptical polarization, with adirection angle of λ and a ellipticity ratio of tan |ω|. The rotation tothe left or right depends upon whether the point P is in the upper orlower hemisphere. Summarizing these conventions, for the cross-sectionview of elliptical polarization represented by the point P, thefollowing relationships (1) and (2) obtain.α=λ(1)b/a=tan |ω|  (2)The cross-section of monochroic light is generally an ellipse, and theellipse can be represented by the symbols shown in FIG. 3. The angle αformed between the half major axis and the X axis is called thedirection angle of the cross-sectional view, which satisfies therelationship 0°≧α≧−90°. If the ellipticity is the ratio b/a of the twohalf axes and tan⁻¹ b/a=β, then 90°≧β≧−90°.

The orientation of polarized light is right-rotational if 2ω is positiveand left-rotational if 2% is negative. From the above, each point in thePoincare sphere represents light of a different form of polarization.That is, one form of polarized light can be represented by one point onthe Poincare sphere.

Therefore, if left-rotational totally circularly polarized light at theupper pole of the Poincare sphere is shifted in the positive directionby π/2 with a direction angle of λ=0, the point H on the equator of thePoincare sphere will be reached. That is, by shifting circularlypolarized light by π/2, its is changed to horizontal linearly polarizedlight. In the same manner, shifting positively by π will reach the lowerpole, which represents right-rotational totally circularly polarizedlight.

If right-rotational totally circularly polarized light at the lower poleof the Poincare sphere is shifted by π/2 at a direction angle of λ=0,point V on the equator will be reached, this representing verticallinearly polarized light, and shifting by π will result inleft-rotational totally circularly polarized light at the upper pole. Ifthe shift amount is neither π/2 nor π, elliptical polarization results.

The liquid-crystal cell 16 is described below in further detail, withreference made to FIG. 4 and FIG. 5.

The liquid-crystal cell 16, as shown in FIG. 4 is made up of aliquid-crystal layer 22 sandwiched between two substrates 20A and 20B,and pixel electrodes 24A and 24B disposed on the upper surface of thesubstrate 20A as shown in FIG. 4, these being separated from one anotherin the horizontal direction. The direction of the electrical fieldoccurring when a voltage from circuit 26 is applied between the pixelelectrodes 24A and 24B is substantially parallel to the substratesurface, so that the mode is enabled in which the direction of thedirectors D of a larger part of the liquid crystal molecules in theliquid-crystal layer 22 rotate while remaining substantially parallel tothe substrate surface, this being known as the IPS (in-plane switching)mode.

The direction of the liquid crystal directors D in the liquid-crystallayer 22 can be further described as follows. As shown in FIG. 5, in thecondition in which an electrical field is not applied between pixelelectrodes 24A and 24B, the direction of the directors D issubstantially perpendicular to the plane of the drawing and, as shown inFIG. 6, in the condition in which an insulation film is applied betweenthe pixel electrodes 24A and 24B, the directors D of the liquid crystalmove toward the direction which is substantially parallel to the drawingplane.

The dielectric constant anisotropy Δ∈ of the liquid crystal in FIG. 5 isshown as positive, in which case if an electrical field is not appliedbetween pixel electrodes 24A and 24B, the direction of the directors Dof the liquid crystal are substantially parallel to the drawing plane,while if an electrical field is applied between the pixel electrodes 24Aand 24B, the directors D of the liquid crystal move towards a directionthat is substantially perpendicular to the drawing plane.

The change of the directors D of the liquid crystal in the example ofFIG. 1 is one in which, when the polarization condition of thecircularly polarized light incident to the liquid-crystal cell 16 isshifted to linearly polarized light, the direction of the polarizationaxis of the linearly polarized light is changed, this being thedirection angle λ, that is, the longitudinal direction on the Poincaresphere of FIG. 2.

Therefore, for example, horizontal linearly polarized light representedby point H on the equator of the Poincare sphere, by changing thedirectors D of the liquid crystal, is changed to a polarization axisdirection represented by a point that is shifted along the equator.

For circularly polarized light, a change in the directors D of theliquid crystal changes the direction of the polarization axis. Forexample, left-rotational circularly polarized light represented by theupper pole point on the Poincare sphere, by a change in the directors Dof the liquid crystal, experiences a change in the direction angle λ,and is represented by a point on the equator shifted in the latitudinaldirection.

The liquid-crystal layer 22 is adjusted so as to have a retardationvalue that shifts the phase of transmitted light by substantially π/2,and the retardation value is substantially the same, regardless ofwhether or not an electrical field is applied between the pixelelectrodes 24A and 24B. This adjustment can be performed, for example,by a known liquid crystal, for example a nematic (Nn) liquid crystal, bycontrol of the birefringence and thickness of the liquid-crystal layer.The director D are substantially parallel to the substrates 20A and 20B.

The above-noted expressions “(shifted) substantially π/2” and“substantially parallel to the substrates 20A and 20B”, include thecases in which there is a slight shift from the ideal condition, becauseof a pre-tilt angle in the liquid crystal or various externaldisturbances.

As noted above, the circular polarization separation layer 14 is made,for example, of a cholesteric liquid-crystal layer. This cholestericliquid-crystal layer exhibits, by virtue of physical molecularorientation, rotation selectivity which separates a light component ofone rotational direction from a light component of the oppositerotational direction, light that is incident to the helical axis of aplanar arrangement being separated into right-rotational andleft-rotational circularly polarized lights, one being transmitted, andthe other being reflected.

This phenomenon is known as circular polarization dichroicity, and ifthe rotation direction with respect to the incident light is selectedappropriately, circularly polarized light having a rotational directionthe same as the helical axis direction of the cholesteric liquid crystalis selectively scattered and reflected.

The maximum rotated light scattering in this case occurs at a wavelengthof λ0 given by Equation (3).λ0=nav·p  (3)

In the above, p is the helical pitch, and nav is the average index ofrefraction within a plane perpendicular to the helical axis.

Under these conditions, the wavelength bandwidth Δλ of the reflectedlight is given by Equation (4).Δλ=λn·p  (4)

In the above, Δn=n(∥)−n (right angle), where n(∥) is the maximum indexof refraction in a plane perpendicular to the helical axis, and n (rightangle) is the maximum index of refraction in a plane parallel to thehelical axis.

Methods of achieving a wide wavelength bandwidth Δλ include a method ofchanging the helical pitch (for example, in U.S. Pat. No. 5,691,789) anda method of superposing a number of cholesteric liquid-crystal layershaving different pitches (in Japanese Unexamined Patent Applicationpublication H9-304770).

It is known that that wavelength λφ of selectively scattered light oflight incident at an inclination to the helical axis of a planararrangement is shifted toward the short wavelength in comparison withλ0.

As a cholesteric liquid crystal material, it is desirable to use achiral nematic liquid crystal with a Shiff's base, an azo compound, anester, or a biphenyl nematic liquid crystal compound, with an opticallyactivated 2-methyl butyl group, a 2-methyl butoxy group, a 4-methylhexyl group joined to an end group thereof, or a chiral reactive liquidcrystal compound.

Whereas a general high-polymer liquid crystal is a high polymer in whicha mesogen group is introduced in the main chain, the side chain, or themain and side chain positions, a high-polymer cholesteric liquid crystalis obtained by introducing a cholesteryl group, for example, into theside chain.

The polarization separation action of a cholesteric liquid crystal isone whereby one circularly polarized light component, either right- orleft-rotational, is transmitted, the other component being reflected.Upon reflection, the right or left circularly polarized light isreflected as is as right or left circularly polarized light.

The light source 12 is a white transparent thin-film planar lightsource, such as a thin-film electroluminescent source sandwiched betweentransparent resin sheets having electrodes, for example, and as notedabove a reflective layer 12A made of, for example, a metal thin film isprovided on the rear surface thereof.

In a liquid-crystal display 10 such as described above, of non-polarizedlight emitted from the light source 12, a circularly polarized lightcomponent of one rotational direction only is transmitted through thecircular polarization separation layer 14, thereby reaching theliquid-crystal cell 16.

For example, of the setting is made such that, as in FIG. 1, onlyleft-rotational circularly polarized light is transmitted, theright-rotational circularly polarized light is reflected at the circularpolarization separation layer 14, the phase being reversed when it isreflected at the reflective layer 12A of the light source 12, or thelight being scattered within the light source (by, for example, alight-scattering function thereof), thereby becoming left-rotationalcircularly polarized light that is transmitted through the circularpolarization separation layer 14, and that strikes the liquid-crystalcell 16.

Left-rotational circularly polarized light transmitted through theliquid-crystal cell 16 is shifted by π/2 when passing therethrough,regardless of whether or not an electrical field is applied. Therefore,circularly polarized light incident to the liquid-crystal cell 16 exitsfrom the liquid-crystal cell 16 as linearly polarized light.

Described in terms of the Poincare sphere of FIG. 2, if a shift is madefrom the upper pole point of the Poincare sphere with a direction angleof λ=0, the result is that left-rotational circularly polarized lightbecomes horizontal linearly polarized light (point H), and if the shiftis made with a direction angle of λ=90°, it becomes vertical linearlypolarized light (point V).

Thus, by applying an electrical field to the liquid-crystal layer 22 inthe liquid-crystal cell 16 from the pixel electrodes 24A and 24B, it ispossible to maintain the retardation value while changing the directionand the directors D of the liquid crystal, so that the polarization axisof transmitted polarized light is caused to change.

On the Poincare sphere of FIG. 2, as a result of a phase shift of π/2,vertical linearly polarized light indicated by the point V on theequator is changes to linearly polarized light having an inclinationindicated a point that is shift along the equator.

In the case of light incident to the liquid-crystal layer 22, it isdesirable to provide a circuit 26 that controls the voltage between theelectrodes so that the direction of the directors of the liquid crystalis changed substantially −45° to +45° with respect to the transmissionaxis of the dichroic linear polarization separation layer as areference.

The dichroic linear polarization separation layer 18 is made of adichroic polarizing material such as Polaroid™, which passes polarizedlight having the transmission axis direction and absorbs almost alllight of a direction that is perpendicular to the transmission axis.

By causing the polarized light transmission axis of the dichroic linearpolarization separation layer 18 so that it either coincides with or isperpendicular to the polarization axis of linearly polarized lightexiting from the liquid-crystal cell 16, and using the circuit 26 tocontrol the electrical field applied to the liquid-crystal layer 22, andparticularly by controlling the electrical field so that the directionof the liquid crystal is controlled so that the direction is changedsubstantially from −45° to +45° with respect to the linearly polarizedlight transmission axis of the dichroic linear polarization separationlayer 18 as a reference, it is possible to adjust the amount of lighttransmitting through the dichroic linear polarization separation layer18 from the maximum amount to the minimum amount, thereby making itpossible to achieve a good display function, such as a gray-scaledisplay function.

This can be expressed by Equation (5).I=I _(o) sin² 2θ(V)sin² (πdΔn/λ)  (5).

In the above, θ(V) is the rotational angle of the liquid crystalmolecules, I is the intensity of light transmitted through the dichroiclinear polarization separation layer 18, I_(o) is the intensity ofincident light, θ is the angle formed between the liquid crystal longaxis (light axis) and the incident polarization direction, Δn and n arethe index of refraction of the liquid crystal and the cell thickness,respectively, and Δ is the wavelength of the incident light.

Further, while FIG. 1 shows the so-called bright display condition, inwhich linearly polarized light exits from the dichroic linearpolarization separation layer, as shown in FIG. 7 if the direction ofthe directors D of the liquid crystal in the liquid-crystal cell 16 ischanged to a direction that is perpendicular to the direction at whichthe linearly polarized light exits from the liquid-crystal cell 16, theso-called dark display condition occurs.

Because the dichroic linear polarization layer 18, is made up of alight-absorbing type of dichroic polarizer, even if external light(non-polarized light) strikes the surface of the dichroic linearpolarization layer 18, 50% thereof is absorbed, and the remaining 50% istransmitted, so that there is almost no reflected component, the resultbeing that it is possible to greatly suppress the decrease in screencontrast in the liquid-crystal display 10.

In FIG. 1 and FIG. 7, as shown by the double-dot-dash line, it isfurther possible to provide an auxiliary dichroic circularly polarizinglayer 13 between the circular polarization separation layer 14 and theliquid-crystal cell 16, so that right-rotational or left-rotationalcircularly polarized light that is transmitted through the circularpolarization separation layer 14 is transmitted, and the othercircularly polarized light component is absorbed.

The auxiliary circular polarization layer 13 is formed by a method oflaminating a λ/4 phase-shifting layer (plate) 35 onto a dichroic linearpolarizing layer 18A having the same configuration as the dichroiclinear polarization layer 18, so that linearly polarized light is causedto be incident at an angle of 45° to the lead or lag axis within theplane of the λ/4 phase-shifting layer 35, onto the liquid-crystal cell16 and linear polarization separation layer 14, so that, of the incidentlight, either right-rotational or left-rotational circularly polarizedlight is transmitted, with the other circularly polarized lightcomponent being almost entirely absorbed.

The λ/4 phase-shifting layer (plate) 35 can also be made of a liquidcrystal material or an inorganic material, as long as it has effect ofshifting the phase of light by λ/4, but it is preferable from thestandpoint of good manufacturability, to use a high polymer resinextended film (extension ratio of approximately 1.3 to 1.4) PC, PVA, PS,PMMA, Norbornene resin or the like.

To achieve a wideband λ/4 phase-shifting plate that shifts the phase oflight over the wavelength range of visible light, it is possible tocause dispose a λ/4 phase-shifting plate and a λ/2 phase-shifting plateso that the phase-lead axis and phase-lag axis thereof intersect at anangle of 60° ±10°, with the λ/2 disposed on the polarizer side. Whenthis is done, the relationship of the transmission axis of the polarizerwith the lead axis or lag axis of the λ/2 phase-shifting plate isappropriately adjusted so that the circularly polarized light incidentto the λ/4 phase-shifting plate is transmitted with maximum intensity,and that circularly polarized light of the opposite polarizationdirection is transmitted with the minimum intensity.

If the above is done, right-rotational or left-rotational circularlypolarized light transmitted through the circular polarization separationlayer 14 passes through the auxiliary dichroic circular polarizationlayer 13, whereupon the other circularly polarized light component thatcould not be reflected at the circular polarization separation layer 14is absorbed by the auxiliary dichroic circular polarization layer 13, sothat the other circularly polarized light component does not reach theliquid-crystal cell 16. Thus, an extremely high contrast condition isobtained.

For example, as shown in FIG. 1, if the setting is made so that onlyleft-rotational circularly polarized light is transmitted, theright-rotational circularly polarized light is reflected at the circularpolarization separation layer 14, and when it is reflected a the lightsource reflective layer 12A, the phase thereof is reversed, or the phaseis scattered within the light source 12 (by, for example, alight-scattering function thereof), thereby being left-rotationalcircularly polarized light that is transmitted through the circularpolarization separation layer 14 and that strikes the liquid-crystalcell 16.

Next a liquid-crystal display 30 according to a second embodiment of thepresent invention is described below, with reference being made to FIG.8.

In FIG. 8, elements having corresponding elements in the liquid-crystaldisplay 10 of FIG. 1 are assigned the same reference numerals and willnot be explicitly described herein.

The liquid-crystal display 30 is formed by a light source 12, a linearpolarization separation layer 32 which, of light exiting from the lightsource 12, transmits one linearly polarized light and reflects anotherlinearly polarized light component that is perpendicular thereto, aliquid-crystal cell 16, and a light-absorption type dichroic circularpolarization layer 34 that receives light having been transmittedthrough the liquid-crystal cell 16.

The linear polarization separation layer 32 can be a planar multilayerstructure of three or more films having birefringence, wherein of twolights having oscillation directions mutually perpendicular within theplane of each layer, the difference in index of refraction betweenlayers adjacent in the thickness direction with respect to one light isdifferent from the difference in index of refraction between layersadjacent in the thickness direction with respect to the other light.

A film having birefringence such as noted above is disclosed, forexample, in the Japanese Unexamined Patent Application publicationH3-75705 and in PCT (WO) H9-506837, can be obtained by extending asubstance exhibiting intraplanar birefringence (index of refractionanisotropy), such as a polycarbonate resin, a polyester resin (forexample, crystalline naphthalene dicarbonic acid polyester), a polyvinylalcohol resin, or a acetic acid cellulose resin or the like.

For example, The index of refraction with respect to a light havingoscillation in the X-axis direction of neighboring birefringent layers(films) is substantially the same nx, the difference in index ofrefraction Δnx(=|nx−nx|) between neighboring layers in the X-axisdirection being substantially zero.

In contrast to, this, for example, if the indices of refraction withrespect to light having oscillation in the Y-axis direction of the firstand third films of a 3-layer birefringent film are both ny₁ and theindex of refraction in the same direction in the second film isny₂(≠ny₁), the index of refraction Δny between neighboring films in theY-axis direction is not substantially zero.

The reflection of light oscillating in the direction in which the indexof refraction difference is large (i.e., the Y-axis direction) isgreater than the reflection of light oscillating in the direction inwhich the index of refraction difference is small (i.e., the X-axisdirection), and the transmission of light in the X-axis direction isgreater than transmission in the Y-axis direction.

For this reason, as seen from light oscillating in the X-axis direction,even if the linear polarization separation layer 32 has a planarmultilayer structure, because the index of refraction in each layer issubstantially same, there is only a slight surface reflection at twolocations, the plane of incidence to the linear polarization separationlayer 32 and the plane of exit therefrom.

In contrast to this, as seen from light oscillating in the Y-axisdirection, because the index of refraction differs in each layer withinthe planar multilayer structure, in addition to the plane of incidenceto and plane of exit from the linear polarization separation layer 32,reflection occurs as well at the surfaces (boundaries) between each ofthe layers, so that the greater the number of layers is, the more timeslight oscillating in the Y-axis direction is reflected.

The dichroic circular polarization layer 34 is formed by a method, forexample, of laminating a λ/4 phase-shifting layer 35 to the dichroiclinear polarization layer 18 on the side of the liquid-crystal cell 16.

In the liquid-crystal display 30, of the unpolarized light from thelight source 12, one linearly polarized light component is transmittedat the linear polarization separation layer 32, and a linearly polarizedlight component perpendicular thereto is reflected.

The reflected linearly polarized light component is reflected either atthe reflective layer 12A of the light source 12 or within the lightsource (by, for example, a light-scattering function thereof), so thatthe component transmitted through the linear polarization separationlayer 32 is increased.

Linearly polarized light that strikes the linear polarization separationlayer 32 is incident to the liquid-crystal layer 22, at which, in thecase in which the direction of the electrical field vector of thelinearly polarized light substantially forms an angle of 45° with thedirection of the directors of the liquid-crystal layer (that is, thecase in which the linearly polarized light is incident at an angle of45° with respect to either the phase-lag axis direction or thephase-lead axis direction of the liquid-crystal layer), the phasethereof is shifted substantially π/2, so that the light becomescircularly polarized light. At the auxiliary dichroic linearpolarization layer 15, linearly polarized light that is perpendicular tothe transmitted linearly polarized light is absorbed, thereby increasingthe purity of the transmitted component.

Described in terms of the Poincare sphere of FIG. 2, for example, avertical linearly polarized light perpendicular represented by theposition of a point V on the equator is shifted by π/2 in the positivedirection, thereby becoming left-rotational circularly polarized light,and horizontal linearly polarized light represented by a point H on theequator is shifted by π/2 in the positive direction, thereby becomingright-rotational circularly polarized light represented by the lowerpole point of the Poincare sphere.

According to the electrical field applied to the liquid-crystal layer22, linearly polarized light becomes, because of a change in the angleof incidence with respect to the phase-lag axis direction or phase-leadaxis direction of the liquid-crystal layer, circularly polarized lightwith a modulated ellipticity. Describing this in terms of the Poincaresphere of FIG. 2, when linearly polarized light changes to circularlypolarized light, there is modulation in the longitudinal direction onthe Poincare sphere, with the ellipticity of the circularly polarizedlight changing.

For example, in the case in which the angle of incidence of linearlypolarized light with respect to the phase-lag axis direction or thephase-lead axis direction of the liquid-crystal layer is zero, linearlypolarized light incident to the liquid-crystal layer remains as linearlypolarized light. However, in the case in which the angle of incidence oflinearly polarized light with respect to the phase-lag axis direction orphase-lead axis direction is −45°, the linearly polarized light incidentto the liquid-crystal layer becomes circularly polarized light with arotation direction the opposite of the above-noted circularly polarizedlight.

That is, the circuit 26 is configured so that, in the case in whichlinearly polarized light strikes the liquid-crystal layer 22, itcontrols the voltage between the electrodes so as to vary the directordirection of the liquid crystal substantially from −45° to +45°, withrespect to the electrical field vector direction of the incidentlinearly polarized light as a reference.

Therefore, by controlling the voltage applied to the liquid-crystallayer 22 from the pixel electrodes 24A and 24B, it is possible to adjustthe amount of light passing through the dichroic circular polarizationlayer 34, thereby enabling a gray-scale display. When this is done,circularly polarized light that is not transmitted through the dichroiccircular polarization layer 34, for example, the left-rotationalcircularly polarized light in FIG. 8, is absorbed thereby.

If right-rotational circularly polarized light is transmitted throughthe dichroic circular polarization layer 34 from the bottom, it is firstconverted to linearly polarized light by the λ/4 phase-shifting layer35, after which it passes through the dichroic linear polarization layer18, and exits as horizontal linearly polarized light.

In the above-noted liquid-crystal display 30, in the case in which noelectrical field is applied to the liquid-crystal layer 22 of theliquid-crystal cell 16, as shown in FIG. 9, linearly polarized lightstriking the liquid-crystal cell 16 is adjusted to left-rotationalcircularly polarized light, so that the so-called dark display conditionoccurs.

In this liquid-crystal display 30, even if unpolarized external lightstrikes the dichroic circular polarization layer 34, 50% thereof isabsorbed, making it possible to suppress a loss of screen contrastcaused by reflection.

It is possible, as shown by the two-dot-dash line in FIG. 8 and FIG. 9,to dispose a light-absorption type auxiliary dichroic linearpolarization separation layer 15 between the linear polarizationseparation layer 32 and the liquid-crystal cell 16.

This auxiliary dichroic linear polarization layer 15 has the sameconfiguration as the dichroic linear polarization layer 18, transmittinglinearly polarized light that has passed through the linear polarizationseparation layer 32 and absorbing a linearly polarized lightperpendicular thereto, which could not be reflected at the linearpolarization separation layer 32.

By doing this, perpendicular linearly polarized light components thatcould not be reflected at the linear polarization separation layer 32are absorbed by the auxiliary dichroic linear polarization layer 15, sothat unnecessary polarized light components do not reach theliquid-crystal cell 16. Thus, it is possible to obtain a displaycondition with extremely good contrast.

While both the above-noted liquid-crystal displays 10 and 30 aretransmissive type displays, it will be understood that the presentinvention is not restricted in this manner, and can be applied as wellto a reflective type liquid-crystal display.

The liquid-crystal display 40 of FIG. 10 is liquid-crystal display 10 ofFIG. 1, except that this is made a reflective type display, wherein alight-absorbing layer 36 is provided in place of the light source 12 ofFIG. 1.

Other aspects and elements of the configuration are the same as theliquid-crystal display 10 of FIG. 1, with corresponding elementsassigned the same reference numerals, and not explicitly describedherein. The auxiliary dichroic circular polarization layer 13 to beexplained below is set so as to transmit left-rotational circularlypolarized light, and the circular polarization separation layer 14 isset so as to reflect left-rotational circularly polarized light.

In this configuration, the light-absorbing layer 36 is, for example, ablack paper, or a resin sheet, film, thin film, or the like, the surfaceof which has been roughened to prevent reflections.

In the above-noted reflective-type liquid-crystal display 40, ofexternal light (unpolarized light), a linearly polarized light componentof one direction, for example horizontal linearly polarized light, istransmitted through the dichroic linear polarization layer 18, andstrikes the liquid-crystal cell 16.

Of the external light, a vertical linearly polarized light componentthat could not pass through the dichroic linear polarization layer 18 isabsorbed thereby. Therefore, because reflection does not occur, it ispossible to suppress the loss of contrast caused by reflections.

A linearly polarized light incident from the dichroic linearpolarization layer 18 has its polarization axis modulated by theelectrical field applied to the liquid-crystal cell 16. As describedwith regard to the liquid-crystal layer 22, this layer has a retardationvalue that causes a phase shift of substantially π/2 in the transmittedlight, so that it has the effect of converting linearly polarized lightby shifting it to circularly polarized light.

The rotational direction of this circularly polarized light isestablished by the above-described modulation of the polarization axisand when it strikes the circular polarization separation layer 14,reflection occurs if the rotational direction is left, but transmissionoccurs if the rotational direction is right.

Described in terms of the Poincare sphere of FIG. 2, horizontal linearlypolarized incident light, by changing the liquid crystal director D from−45° to +45°, is moved from the point H on the equator, the move beingfrom the upper pole point to the point H in the case of −45° to 0°, sothat left-rotational circularly polarized light becomes linearlypolarized light, and the move being from the lower pole point to thepoint H in the case of 0 to 45°, so that right-rotational circularlypolarized light become linearly polarized light.

Left-rotational circularly polarized light L reflected by the circularpolarization separation layer 14 returns to the liquid-crystal cell 16from a direction that is the opposite of that noted above, and when thislight passes through the liquid-crystal cell 16, in the same manner asin the liquid-crystal display 10 of FIG. 1, it exits as linearlypolarized light, the polarization axis thereof being modulated by thedirection of the directors D of the liquid crystal, and passes throughthe dichroic linear polarization layer 18 to become display light.Therefore, the amount of light reflected by the circular polarizationseparation layer 14 and passing through the liquid-crystal cell 16 canbe adjusted by means of the voltage applied to the liquid-crystal layer22. That is, it is possible to obtain a gray-scale display by using thismethod.

In the liquid-crystal layer 22, in the case of right-rotationalcircularly polarized light, after a component exiting from theliquid-crystal layer 22 and not reflected by the circular polarizationseparation layer 14 passes therethrough, it is absorbed by thelight-absorbing layer 36 and removed, so that the dark display shown inFIG. 11 occurs. For this reason, in comparison with the left-rotationalcircularly polarized light L reflected by the circular polarizationseparation layer 14 and passing through the liquid-crystal cell 16,there is very good display contrast.

In the liquid-crystal display 40 as well, as shown by the two-dot-dashline of FIG. 10 and FIG. 11, and in the same manner as shown in FIG. 1and FIG. 7, it is possible to dispose the auxiliary dichroic circularpolarization layer 13 between the circular polarization separation layer14 and the liquid-crystal cell 16.

By doing this, when light transmitted through the liquid-crystal cell 16strikes the auxiliary dichroic circular polarization layer 13,left-rotational circularly polarized light is transmitted andright-rotational circularly polarized light is absorbed, so that thereis a further improvement in contrast.

A reflective type liquid-crystal display 50 shown in FIG. 12 isdescribed below.

This liquid-crystal display 50 has, in place of the light source 12 ofthe liquid-crystal display 30 shown in FIG. 8, the light-absorbing layer36 as noted above, and has a modified dichroic circular polarizationlayer 34.

The dichroic circular polarization layer 34 is laminated so as to have aλ/4 phase-shifting layer on the side opposite that of the liquid-crystalcell 16 side in the dichroic linear polarization layer thereof in theliquid-crystal display 10 shown in FIG. 8, the phase-lead axis orphase-lag axis thereof being at an angle of 45° with respect to thetransmission axis of the dichroic linear polarization layer.

In the liquid-crystal display 50, external light (unpolarized light)strikes the dichroic circular polarization layer 34 and onlyright-rotational circularly polarized light R strikes the liquid-crystalcell 16. The other left-rotational circularly polarized light L of theexternal light is absorbed by the dichroic circular polarization layer34, so that there is no decrease in screen contrast caused by reflectedlight.

Because the liquid-crystal layer 22 has a retardation value so as toshift the phase of light substantially π/2, for the right-rotationalcircularly polarized light R striking the liquid-crystal layer 22, interms of the Poincare sphere of FIG. 2, by the application of anelectrical field to the liquid-crystal layer 22, the director Ddirection of the liquid-crystal layer is changed, resulting in a shiftfrom the lower pole point to either the point V or the point H on theequator, representing linearly polarized light, the ellipticity of thecircularly polarized light being modulated.

Therefore, linearly polarized light that has exited from theliquid-crystal cell 16, depending upon its polarization condition, isreflected by the linear polarization separation layer 32 or absorbedthereby. Thus, a high contrast condition is obtained.

In the example of FIG. 12, only a vertical linearly polarized lightcomponent is reflected by the linear polarization separation layer 32 soas to strike the liquid-crystal cell 16 once again, this being changedby the liquid-crystal layer to left-rotational circularly polarizedlight, which cannot pass through the dichroic circular polarizationlayer 34, so that the display does not become bright.

As shown in FIG. 13, when only vertical linearly polarized light exitsfrom the liquid-crystal cell 16, this light passes through the linearpolarization separation layer 32, and is absorbed by the light-absorbinglayer 36, so that the dark display condition occurs.

In the aforementioned embodiments, the light source 12 is a transparentthin-film white planar light source made of a thin-filmelectroluminescent sources sandwiched between transparent resin sheetshaving transparent electrodes, with a reflective layer 12A made of, forexample, a metal thin film provided on the rear thereof. It will beunderstood, however, that the present invention is not restricted inthis manner, and can also use an edge-light type white planar lightsource in which light from a light source incident from a side edge of alight-guide sheet is caused exit one surface of the light-guide sheet,for example, by disposing a linear light source on a light-guide sheet.In this case, a reflective layer made of a metal thin film or the likeis disposed on the other side of the light-guide sheet, and it is alsopossible to use white PET (polyethylene teraphthalate).

It is also possible to laminate a phase-shifting layer with aretardation value such that the phase of transmitted light is shiftedsubstantially by π/2 on the circular polarization separation layer orlinear polarization separation layer, the result being that thislaminate has the same effect as a linear polarization separation layeror a circular polarization separation layer.

In general, there are two modes in a liquid crystal panel, one being thenormally white mode, in which, depending upon the angle (directionangle) of the transmission axis of the dichroic polarizer with respectto the liquid crystal, light is transmitted when voltage is not appliedto the liquid crystal, and the normally black mode, in which, light isnot transmitted when there is no voltage applied to the liquid crystal,and it should be understood that the present invention can be applied toboth the normally white mode and the normally black mode.

In the liquid-crystal display 50 as well, as shown by the two-dot-dashlines of FIG. 12 and FIG. 13, and similar to the case shown in FIG. 8and FIG. 9, can have the auxiliary dichroic linear polarization layer 15disposed between the linear polarization separation layer 32 and theliquid-crystal cell 16.

If this is done, linearly polarized light exiting from theliquid-crystal cell 16, if the polarization condition is vertical,absorbed by the auxiliary dichroic linear polarization layer 15, theremaining non-absorbed light being entirely absorbed by thelight-absorbing layer 36, so that there is a further improvement in thecontrast.

Referring to FIG. 14, a liquid-crystal display 60 according to the fifthembodiment of the present invention has the light source 12, thecircular polarization separation layer 14, a liquid-crystal cell 62having a retardation value that changes with application of anelectrical field to the liquid crystal, and which acts to shift thephase of incident circularly polarized light substantially 0 to π, andthe light-absorbing type dichroic circular polarization layer 34disposed on the side of the liquid-crystal cell 62 opposite from thecircular polarization separation layer 14, which receives circularlypolarized light that has been transmitted through the liquid-crystalcell 62.

In FIG. 14, elements corresponding to elements shown in FIG. 1, FIG. 4,and FIG. 9 have been assigned the same reference numerals and are notexplicitly described herein.

The liquid-crystal cell 62, as shown in FIG. 15, is formed by aliquid-crystal layer 64 sandwiched between two substrates 20A and 20B asshown in FIG. 15, and a pair of pixel electrodes 64A and 64B disposed onthe lower surface of the upper substrate 20A and the upper surface ofthe lower substrate 20B, and which sandwich the liquid-crystal layer 64in the thickness direction.

The liquid-crystal layer 64 in the liquid-crystal cell 62 has a liquidcrystal retardation value that changes with the application of anelectrical field from the pixel electrodes 64A and 64B, this beingadjusted so that the phase of circularly polarized incident lightpassing through the circular polarization separation layer 14 and theauxiliary dichroic circular polarization layer 13 is shiftedsubstantially 0 to π.

This adjustment can be done by various known liquid crystals, by controlof the birefringence and thickness of the liquid-crystal layer 64.

Such liquid crystals are known as ECB (electrically controlledbirefringence) liquid crystals, and have modes such as a DAP(deformation of vertical aligned phases) mode, a HAN (hybrid alignednematic) mode, an STN (super twisted nematic) mode, an SBE (supertwisted birefringence effect) mode, an SSGLC (surface stabilizedferroelectric liquid crystal) mode, an OCB (optically compensated bend)mode, and a VAN (vertically aligned nematic) mode.

While the OCB mode usually refers to a mode in which a bend alignedliquid-crystal layer and a biaxial phase shifting sheet are sandwichedbetween light-absorbing type dichroic linear polarizing sheets havinglight-absorbing axes that are mutually perpendicular, with regard to thepresent invention, the term will be used to refer to the bend alignedliquid-crystal cell only.

Similarly, while the VAN mode usually refers to a mode in which a VANaligned cell of vertically sandwiched nematic liquid crystals issandwiched between light-absorbing type dichroic linear polarizingsheets having light-absorbing axes that are mutually perpendicular, withregard to the present invention, the term will be used to refer to theVAN aligned liquid-crystal cell only.

The other modes are similar.

While the term ECB is often used to refer to a color display methodwhich makes uses of birefringence, with regard to the present inventionthe term will be used to refer to a mode in which the birefringencevalue of a liquid-crystal layer changes.

The expression “shift the phase substantially 0 to π” refers tosubstantially changing the phase at the liquid-crystal layer 64 itself,or to the use of a phase shifting layer separate from the liquid-crystalcell 62, this being formed between the liquid-crystal cell 62 and theabove-noted first dichroic circular polarization layer 34 and/or betweenthe liquid-crystal cell 62 and the circular polarization separationlayer 14, the mutual interaction between the liquid-crystal layer 64 andthe phase-shifting layer acting to substantially shift the phase oflight passing therethrough by 0 to π.

For example, by changing the retardation value o the liquid-crystallayer 64 itself from 0.1π to 1.1π, or by the mutual interaction betweenthe liquid-crystal layer 64 and the dichroic circular polarization layer14 and/or with a phase-shifting layer having a retardation value ofsubstantially 0.1π provided separately on the circular polarizationseparation layer 14 causes the phase of light passing therethrough toshift substantially from 0 to π.

The above-noted mutual interaction is the action that occurs, forexample, when lead axis or lag axis of a phase shifting layer having aretardation value of substantially 0.1π is caused to intersectperpendicularly with the lead axis or lag axis of a liquid-crystal layerwhen the retardation thereof is 0.1π or 1.1π. For example, thecalculations would be 0.1π−0.1π=0, and 1.1π−0.1π=π.

It will be understood that the action of changing the phasesubstantially from −π to 0 is also within the scope of the presentinvention.

When the phase of circularly polarized light is shifted by π, it ischanged to circular polarization layer of the opposite rotationaldirection.

In the liquid-crystal display 60, of the unpolarized light exiting fromthe light source 12, for example as shown in FIG. 14 a left-rotationalcircularly polarized light component L is transmitted through thecircular polarization separation layer 14 and reaches the liquid-crystalcell 62.

The other, right-rotational circularly polarized light component R isreflected at the circular polarization separation layer 14, and when itis reflected by the reflective layer 12A of the light source 12 itsphase is reversed or it becomes unpolarized, becoming left-rotationalcircularly polarized light passing through the circular polarizationseparation layer 14 which then strikes the liquid-crystal cell 62.

By applying a voltage to the liquid-crystal layer 64 of theliquid-crystal cell 62 from the pixel electrodes 64A and 64B, theretardation value is caused to change, thereby shifting the phase of thelight transmitted through the liquid-crystal cell 62 substantially 0 toπ by the application of an electrical field. Therefore, whenleft-rotational circularly polarized light L striking the liquid-crystalcell 62 undergoes the maximum shift of π, it becomes right-rotationalcircularly polarized light R with a reversed rotational direction, andexits from the liquid-crystal cell 62.

If the polarization transmission axis of the dichroic circularpolarization layer 34 is made to coincide with one of the two rotationaldirections, for example, with right rotation, by controlling anelectrical field applied to the liquid-crystal layer 64, it is possibleto adjust the amount of right-rotational circularly polarized light Rthat passes through the dichroic circular polarization layer 34, therebyachieving a liquid crystal display function.

Describing this in terms of the Poincare sphere of FIG. 2, with a shiftfrom the upper pole point on the Poincare sphere of 0 to π/2, π/2, andπ/2 to π, via a point H on the equator, with a direction angle of λ=0,left-rotational circularly polarized light changes to left-rotationalelliptically polarized light, then horizontal linearly polarized light,right-rotational elliptically polarized light, and finallyright-rotational circularly polarized light.

Therefore, in the shift range from 0 to π/2, the dark display conditionsuch as shown in FIG. 16 occurs, and in the shift range from π/2 to π,the larger the shift amount is the more light passes through thedichroic circular polarization layer 34, thereby enabling a gray-scaledisplay.

Because the dichroic circular polarization layer 34 is a light-absorbingtype dichroic polarizer, even if external (unpolarized) light strikesthe surface thereof, 50% of the light is absorbed, and the remaining 50%is transmitted, so that there is almost no reflected component, therebyenabling a great suppression of a reduction in screen contrast in theliquid-crystal display 60.

By using the brirefringence of the liquid-crystal layer 64, it ispossible to achieve a color liquid crystal display function withouthaving to provide a separate color filter.

In the liquid-crystal display 60 as well, the auxiliary dichroiccircular polarization layer 13 can be disposed between the circularpolarization separation layer 14 and the liquid-crystal cell 62.

By doing this, right-rotational circularly polarized light R that wasnot reflected by the circular polarization separation layer 14 isabsorbed by the auxiliary dichroic circular polarization layer 13.Therefore, it is possible to achieve a condition with extremely goodcontrast.

A liquid-crystal display 70 according to the sixth embodiment of thepresent invention and shown in FIG. 17 is described below.

The liquid-crystal display 70 has the light source 12, the linearpolarization separation layer 32, which of light exiting from the lightsource 12 transmits one linearly polarized light component and reflectsa linearly polarized light component perpendicular thereto, theliquid-crystal cell 62, and the light-absorption type dichroic linearpolarization layer 18 that receives polarized light that has beentransmitted through the liquid-crystal cell 62.

In the liquid-crystal display 70, one linearly polarized light componentof unpolarized light from the light source is transmitted by the linearpolarization separation layer 32, and a linearly polarized lightcomponent perpendicular thereto is reflected.

When the reflected linearly polarized light component is reflected bythe reflective layer 12A of the light source 12, a light scatteringsheet or the like disposed in the light path (not shown in the drawing)changes it to unpolarized light, which passes through the linearpolarization separation layer 32.

Linearly polarized light that has passed through the linear polarizationseparation layer 32 strikes the liquid-crystal layer 64 at which, by theaction of an electrical field, the phase thereof is shiftedsubstantially 0 to π.

If the phase of linearly polarized light is shifted by π, it becomeslinearly polarized light of a direction that is perpendicular to theabove-noted linearly polarized light.

Described in terms of the Poincare sphere of FIG. 2, with a shift from apoint H on the equator of the Poincare sphere of 0 to π with a directionangle of λ=0, horizontal linearly polarized light becomesleft-rotational elliptically polarized light, then right-rotationalcircularly polarized light, then right-rotational elliptically polarizedlight, and finally vertical linearly polarized light. Therefore, thelarger is the amount of shift, the smaller is the amount of lightpassing through the dichroic circular polarization layer. The darkdisplay condition is shown in FIG. 18.

Therefore, by controlling the voltage applied to the liquid-crystallayer 64 from the pixel electrodes 64A and 64B, it is possible to adjustthe amount of light transmitted through the dichroic linear polarizationlayer 18. That is, it is possible to achieve a liquid crystal displayfunction with gray-scale capability.

This can be represented by Equation (6).I=I ₀ sin² 2θ sin² (πdΔn(V)/λ)  (6)

In the above, I is the intensity of light transmitted through thedichroic linear polarization layer 18, I₀ is the intensity of incidentlight, θ is the angle formed between the incident light direction andthe normal light oscillation direction in the liquid-crystal cell, Δn(V)and d are the birefringence at an applied voltage of V an the cellthickness, and λ is the wavelength of the incident light.

In the liquid-crystal display 70, even if unpolarized external light isreceived, the dichroic linear polarization layer 18 absorbs 50% thereof,so that it is possible to suppress the reduction in screen contrastcaused by reflection.

In the liquid-crystal display 70 as well, an auxiliary dichroic linearpolarization layer 15 can be disposed between the linear polarizationseparation layer 32 and the liquid-crystal cell 62. The action of thisauxiliary linear polarization separation layer 15 is the same asdescribed above.

While both the above-noted liquid-crystal displays 60 and 70 aretransmissive types, it will be understood that the present invention isnot restricted in this manner, and can be applied as well to areflective type of liquid-crystal display.

The liquid-crystal display 80 shown in FIG. 19 is the liquid-crystaldisplay 60 of FIG. 14, except that is made a reflective type, in whichthe light-absorbing layer 36 is provided in place of the light source 12of FIG. 14.

Other aspects and elements of the configuration are the same as theliquid-crystal display 60 shown in FIG. 14 and corresponding elementshave been assigned the same reference numerals, and are not explicitlydescribed herein. The dichroic circular polarization layer 34 is set soas to transmit right-rotational circularly polarized light and thecircular polarization separation layer 14 is set so as to reflectleft-rotational circularly polarized light.

In this reflective type liquid-crystal display 80, external(unpolarized) light strikes the dichroic circular polarization layer 34and, of the right-rotational and left-rotational circularly polarizedlight components, right-rotational circularly polarized light R strikesthe liquid-crystal cell 62. The other circularly polarized lightcomponent of the incident light, that is, the left-rotational circularlypolarized light L is absorbed by the dichroic circular polarizationlayer 34, so that there is no reduction in screen contrast by reflectedlight.

The polarization axis of right-rotational circularly polarized light Rstriking the liquid-crystal layer 62, in accordance with a liquidcrystal retardation value that varies with a change in the electricalfield applied to the liquid-crystal cell 62, is shifted substantially 0to π.

Described in terms of the Poincare sphere of FIG. 2, as shown in FIG.19, if right-rotational circularly polarized light striking theliquid-crystal cell 62, on the Poincare sphere of FIG. 2, is shiftedfrom the lower pole by a shift amount of 0 to π/2, it becomesright-rotational elliptically polarized light, If the shift amount isπ/2 the shift is to the point V on the equator, this representingvertical linearly polarized light, if the shift amount is π/2 to π, theshift is to the upper hemisphere, representing left-rotationalelliptically polarized light, and if the shift amount is π, the lightexits the liquid-crystal cell 62 as circularly polarized light.

In this manner, the rotational direction of the circularly polarizedlight is established by modulation of the polarization axis, and whenlight strikes the circular polarization separation layer 14, it isreflected if the rotational direction is left and transmitted if therotational direction is right.

Therefore, it is possible to adjust the amount of light reflected fromthe circular polarization separation layer 14 and passed through theliquid-crystal cell 16 by means of the voltage applied to theliquid-crystal layer 64.

Left-rotational circularly polarized light L reflected at the circularpolarization separation layer 14 returns to the liquid-crystal cell 62with the same rotational direction as noted above, the polarization axisbeing again modulated by 0 to π, it thereby becoming right-rotationalcircularly or elliptically polarized light, which exits via the dichroiccircular polarization layer 34 and becomes display light, while apolarized light component that has exited from the liquid-crystal layer64 and passed through the circular polarization separation layer 14(included leaking light through the polarizer 35) is, as noted above, asmall amount, this being absorbed and removed by the light-absorbinglayer 36.

For this reason, there is good display contrast in relation to thepolarized light (display light) that has been reflected by the circularpolarization separation layer 14 and transmitted through theliquid-crystal cell 62.

By using the birefringence of the liquid-crystal layer 64, it ispossible to achieve a color liquid-crystal display function, without theneed for a separately provided color filter.

In the liquid-crystal display 80 as well, it is possible to dispose anauxiliary circular polarization layer 13 between the circularpolarization separation layer 14 and the liquid-crystal cell 62.

In this case, at the auxiliary circular polarization layer 13 before thecircular polarization separation layer 14, because right-rotationalcircularly polarized light R of the transmitted light from theliquid-crystal cell 62 is absorbed, there is almost no transmittedcomponent through the circular polarization separation layer 14. Forthis reason, it is possible to achieve a further improvement incontrast.

A reflective type liquid-crystal display 90 shown in FIG. 20 isdescribed below.

The liquid-crystal display 90 has, in place of the light source 12 ofthe liquid-crystal display 70 shown in FIG. 17, the light-absorbinglayer 36.

In the liquid-crystal display 90, when external light (unpolarizedlight) is transmitted through the dichroic linear polarization layer 18,it is changed to linearly polarized light, which strikes theliquid-crystal cell 62. Of the external light, a component which cannotbe transmitted through the dichroic linear polarization layer 18 isabsorbed thereby. Therefore, there is almost no reflected light, makingit possible to suppress a reduction in contrast caused by reflectedlight.

Linearly polarized light that has passed through the dichroic linearpolarization layer 18, in accordance with the liquid-crystal layerretardation value that changes with an electrical field applied to theliquid-crystal layer 64, undergoes a phase shift of substantially 0 toπ.

Described in terms of the Poincare sphere of FIG. 2, horizontal linearlypolarized light, for example, as represented by point H on the equatoris shifted in the positive direction by 0 to π/2, thereby becomingright-rotational elliptically polarized light, is shifted by π/2 tobecome right-rotational totally circularly polarized light representedby the lower pole point on the Poincare sphere, is shifted by π/2 to πto become right-rotational elliptically polarized light, and is shiftedby π to become vertical linearly polarized light.

Therefore, the left-rotational elliptically or circularly polarizedlight exiting from the liquid-crystal cell 62, depending upon thepolarization axis thereof, is reflected at the linear polarizationseparation layer 32, with other light passing through the linearpolarization separation layer 32. Linearly polarized light having passedthrough the linear polarization separation layer 32 returns to theliquid-crystal cell 62 with a direction the opposite of that notedabove, at which point it undergoes a phase shift of substantially 0 toπ, and strikes the dichroic linear polarization layer 18, with only ahorizontal linearly polarized light transmitted. Therefore, a conditionof extremely good contrast is achieved.

It is also possible to have an arrangement in which, when no voltage isapplied to the liquid-crystal layer of the liquid-crystal cell from thepixel electrodes, the phase of light transmitted through theliquid-crystal cell is shifted substantially π/2, and when a voltage isapplied to the electrodes, the phase of light transmitted through theliquid-crystal cell is substantially unshifted.

In the liquid-crystal display 90 as well, it is possible to dispose anauxiliary linear polarization layer 15 between the linear polarizationseparation layer 32 and the liquid-crystal cell 62.

The function of the auxiliary linear polarization layer 15 is as abovedescribed.

As shown in FIG. 21, a liquid-crystal display 100 according to the ninthembodiment of the present invention has the light source 12, thecircular polarization separation layer 14, a liquid-crystal cell 102having a liquid crystal retardation value that changes with theapplication of an electrical field thereto, and which acts to shift thephase of incident light transmitted through the circular polarizationseparation layer 14 by substantially −π/2 to π/2, and thelight-absorption type dichroic linear polarization layer 18 disposed onthe side of the liquid-crystal cell 102 opposite from the circularpolarization separation layer 14 and which receives light that haspassed through the liquid-crystal cell 102.

The liquid-crystal cell 102, as shown in FIG. 22, has a liquid-crystallayer 104 sandwiched between two substrates 20A and 20B, and a pair ofpixel electrodes 104A and 104B disposed on the lower surface of theupper substrate 20A and the upper surface of the lower substrate 20B,which sandwich the liquid-crystal layer 104 in the thickness direction.

The liquid-crystal layer 104 in the liquid-crystal cell 102 has aretardation value that changes with application of an electrical fieldfrom the pixel electrodes 104A and 104B, this being adjusted so as toshift the phase of circularly polarized light that has passed throughthe circular polarization separation layer 14 and auxiliary circularpolarization layer 13 by substantially −π/2 to π/2.

Since the above-noted configuration is the same as the liquid-crystallayer 64 shown in FIG. 15, this adjustment will not be described herein.

The above-noted phrase “shifted . . . substantially −π/2 to π/2” refersto substantially changing the phase at the liquid-crystal layer 102itself, or to the use of a phase shifting layer separate from theliquid-crystal cell 102, this being formed between the liquid-crystalcell 102 and the above-noted dichroic circular polarization layer 34,the mutual interaction between the liquid-crystal layer 104 and thephase-shifting layer acting to substantially shift the phase of lightpassing therethrough by −π/2 to π/2.

For example, if the retardation value of the liquid-crystal layer 104itself is varied from 0 to π, the phase difference between theliquid-crystal layer 104 and the dichroic circular polarization layer 34and/or the mutual interaction with a phase difference which issubstantially a π/2 provided separately in the circular polarizationseparation layer 14 encompasses a shift of substantially −π/2 to π/2 inthe phase of light passing therethrough. The above-noted mutualinteraction is the effect that occurs when, with respect to thephase-lead axis or the phase-lag axis when the retardation value of theliquid-crystal layer is π, the retardation value is substantially π/2,which is the phase-lead axis or phase-lag axis of the phase-shiftinglayer that are caused to intersect perpendicularly, for example, thisbeing calculatable as 0−π/2=−π/2, and π−π/2=π/2.

It will be understood that the use of a liquid-crystal cell having theeffect of shifting the phase by substantially π/2 to −π/2 is encompassedin the present invention.

When the phase of circularly polarized light is shifted by π/2, itbecomes linearly polarized light, and when it is shifted −π/2 it becomeslinearly polarized light that is perpendicular to the above-notedlinearly polarized light. When the phase of linearly polarized light isshifted by π/2 it becomes circularly polarized light, and when it isshifted by −π/2 it becomes circularly polarized light of the oppositerotational direction.

In a liquid-crystal display 100 as described above, of unpolarized lightexiting from the light source 12, circularly polarized light of onerotational direction, for example left-rotational circularly polarizedlight L as shown in FIG. 21 is transmitted through the circularpolarization separation layer 14, so that it reaches the liquid-crystalcell 102.

The other, right-rotational circularly polarized light R is reflected bythe circular polarization separation layer 14, and when it is reflectedby the reflective layer 12A of the light source 12, its phase isreversed, or it becomes unpolarized light, so that the amount ofleft-rotational circularly polarized light L transmitted through thecircular polarization separation layer 14 increases, and strikes theliquid-crystal cell 102.

By applying a voltage from the pixel electrodes 104A and 104B to theliquid-crystal layer 104, the retardation value of the liquid crystal ischanges, so that the circularly polarized light passing through theliquid-crystal cell 102 is shifted by the applied electrical fieldsubstantial by −π/2 to π/2.

Therefore, when the phase of circularly polarized light striking theliquid-crystal cell 12 is shifted by π/2, it becomes linearly polarizedlight, and when it is shifted by −π/2 it becomes linearly polarizedlight of a direction perpendicular thereto, which exits from theliquid-crystal cell 102.

By causing the polarization transmission axis of the dichroic linearpolarization layer 18 to coincide with one of the two polarizationdirections, by controlling the electrical field applied to theliquid-crystal layer 104, it is possible to adjust the amount of lightpassing through the dichroic linear polarization layer 18, therebyenabling a liquid crystal display function and, of course, a gray-scaledisplay as well.

Described in terms of the Poincare sphere of FIG. 2, by shifting to thepoint H on the equator with a direction angle of λ=0 by 0 to π/2 fromthe upper pole point on the Poincare sphere, left-rotational circularlypolarized light is changed to elliptical polarized light, and thenchanged to horizontal linearly polarized light, and if a shift is madefrom the point V on the equator by 0 to −π/2, left-rotational circularlypolarized light becomes vertical linearly polarized light.

Therefore, when amount of shift of 0 to π/2, the larger the amount ofshift is, the greater is the amount of light passing through thedichroic linear polarization layer 18, and with an amount of shift of 0to −π/2, the larger the amount of shift is, the darker is the display,until it finally reaches the dark display shown in FIG. 23.

Because the dichroic linear polarization layer 18 is made of alight-absorption type dichroic polarizer, even if external (unpolarized)light strikes the surface of the dichroic linear polarization layer 18,50% thereof is absorbed, the remaining 50% being transmitted, so thatthere is almost no reflected component, thereby enabling greatsuppression of a loss of screen contrast in the liquid-crystal display100.

By using the birefringence of the liquid-crystal layer 104, it ispossible to achieve a color display function without the need to use aseparate color filter.

In the liquid-crystal display 100 as well, it is possible to dispose theauxiliary dichroic circular polarization layer 13 between the circularpolarization separation layer 14 and the liquid-crystal cell 102.

In this case, at the auxiliary circular polarization layer 13 before thecircular polarization separation layer 14, because right-rotationalcircularly polarized light R of the transmitted light from theliquid-crystal cell 102 is absorbed, there is almost no transmittedcomponent through the circular polarization separation layer 14. Forthis reason, it is possible to achieve a further improvement incontrast.

A liquid-crystal display 110 according to the tenth embodiment of thepresent invention, shown in FIG. 24, is described below.

The liquid-crystal display 110 has the light source 12, the linearpolarization separation layer 32 which, of the light exiting from thelight source 12 transmits a linearly polarized light component of onedirection within the plane of the drawing (which will be taken ashorizontal in this example) and reflects a linearly polarized light of adirection perpendicular thereto, the liquid-crystal cell 102, and thelight-absorption type dichroic circular polarization layer 34, whichreceives polarized light that passes through the liquid-crystal cell102.

In the liquid-crystal display 110, of the unpolarized light from thelight source 12, a horizontal linearly polarized light component istransmitted through the linear polarization separation layer 32 and alinearly polarized light component perpendicular thereto is reflected.

The reflected linearly polarized light component is reflected to thereflective layer 12A of the light source 12 or reflected within thelight source 12 (by, for example, a light scattering function thereof),so that its phase is disturbed, resulting in an increase in thecomponent passing through the linear polarization separation layer 32.

Linearly polarized light having passed through the linear polarizationseparation layer 32 strikes the liquid-crystal cell 102, and has itsphase shifted by the electrical field applied thereto.

By applying a voltage to the liquid-crystal layer 104 from the pixelelectrodes 104A and 104B, the retardation value of the liquid crystal ischanged, thereby shifting linearly polarized light passing through theliquid-crystal cell 102 by the action of the electrical field bysubstantially −π/2 to π/2.

When the phase of linearly polarized light which strikes theliquid-crystal cell 102 is shifted by π/2, it becomes circularlypolarized light, and when it is shifted by −π/2 it becomes circularlypolarized light of the opposite rotational direction, whereupon it exitsfrom the liquid-crystal cell 102.

Described in terms of the Poincare sphere of FIG. 2, if a shift of 0 toπ/2 is made at a direction angle of λ=0 from the point H on the equatorof the Poincare sphere, horizontal linearly polarized light becomesright-rotational elliptically polarized light and then right-rotationalcircularly polarized light. Therefore, the larger the amount of theshift, the greater is the amount of light passing through the dichroiccircular polarization layer 34. If a shift of 0 to π is made from theabove-noted point H, the display will darken according to the amount ofthe shift, until at −π/2 when it reaches the dark display condition asshown in FIG. 25.

By causing the polarization transmission axis of the dichroic circularpolarization layer 34 to coincide with the right-rotational component oftwo rotational directions, similar to the case of the liquid crystalcell 62 of FIG. 14, by controlling the electrical field applied to theliquid-crystal layer 104, it is possible to adjust the amount of lighttransmitted through the dichroic circular polarization layer 18, therebyenabling achievement of a liquid crystal display function and agray-scale display as well.

In the liquid-crystal display 110 as well it is possible to dispose theauxiliary dichroic linear polarization layer 15 between the linearpolarization separation layer 32 and the liquid-crystal cell 102.

In this case, linearly polarized light transmitted through the linearpolarization separation layer 32 passes through the auxiliary dichroiclinear polarization layer 15, and the remaining linearly polarized lightthat is not reflected by the linear polarization separation layer 32 isabsorbed. Therefore, it is possible to achieve an extremely goodcontrast condition.

A liquid-crystal display 120 according to an eleventh embodiment of thepresent invention, shown in FIG. 26, is described below.

The liquid-crystal display 120 shown in FIG. 26 is the liquid-crystaldisplay 100 except that it is a reflective type, in which alight-absorbing layer 36 is provided in place of the light source 12 ofFIG. 21.

Because other aspects and elements of the configuration are the same asthe liquid-crystal display 100 shown in FIG. 21, corresponding elementshave been assigned the same reference numerals, and are not explicitlydescribed herein.

In the reflective type liquid-crystal display 120, external(unpolarized) light strikes the dichroic linear polarization layer 18,at which only horizontal linearly polarized light coinciding with theestablished transmission axis thereof is allowed to strike theliquid-crystal cell 10. The other linearly polarized light component ofthe external light is absorbed by the dichroic linear polarization layer18, so that reflected light is not allowed to reduce the screencontrast.

The phase of horizontal linearly polarized light striking theliquid-crystal cell 102 is shifted by the electrical field applied tothe liquid-crystal layer.

That is, by applying a voltage to the liquid-crystal layer 104 from thepixel electrodes 104A and 104B, the retardation value of the liquidcrystal is changed, so that the phase of linearly polarized lightpassing through the liquid-crystal cell 102 is shifted by the appliedelectrical field substantially −π/2 to π/2.

As described above, when the phase of linearly polarized light strikingthe liquid-crystal cell 102 is shifted by π/2, it becomes linearlypolarized light, and when it is shifted by −π/2 it becomes circularlypolarized light of the opposite rotational direction, whereupon it exitsfrom the liquid-crystal cell 102.

Of circularly polarized light exiting from the liquid-crystal cell 102circularly polarized light of one rotational direction, for example aleft-rotational circularly polarized light L as shown in FIG. 21, istransmitted through the circular polarization separation layer 14, sothat it reaches the light-absorbing layer 36.

The other, right-rotational circularly polarized light R is reflected atthe circular polarization separation layer 14, and strikes theliquid-crystal cell 102 without a change in its phase.

Because, as described above, a voltage is applied to the liquid-crystallayer 104 of the liquid-crystal cell 102 from the pixel electrodes 104Aand 104B, the phase of circularly polarized light that passes throughthe liquid-crystal cell 102 is shifted substantially by −π/2 to π/2 bythe action of the application of an electrical field.

Therefore, when the phase of circularly polarized light incident to theliquid-crystal cell 102 is shifted by π/2, it becomes linearly polarizedlight, and when it is shifted by −π/2, it becomes linearly polarizedlight of the opposite direction, whereupon it exits from theliquid-crystal cell 102.

Because the polarization transmission axis of the dichroic linearpolarization layer 18 is caused to coincide with one of the polarizationdirections of the two directions as noted above, light is transmittedthrough the dichroic linear polarization layer 18 responsive to theinclination of the polarization axis of linearly polarized light exitingfrom the liquid-crystal cell 102, this light being used as the displaylight. Therefore, by controlling the electrical field applied to theliquid-crystal layer 104, it is possible to adjust the amount of lightpassing through the dichroic linear polarization layer 18, so that aliquid crystal display function can be achieved, in addition, of course,to gray-scale display.

It is also possible to have the shift the phase of light transmittedthrough the liquid-crystal cell by π/2 when no voltage is applied to theliquid-crystal cell from the pixel electrodes, and to substantially notshift the phase of light transmitted through the liquid-crystal cellwith voltage applied to the electrodes.

In the liquid-crystal display 120 as well, it is possible to dispose theauxiliary circular polarization layer 13 between the circularpolarization separation layer 14 and the liquid-crystal cell 102.

In this case, a left-rotational circularly polarized light L exitingfrom the liquid-crystal cell 102 is absorbed in the auxiliary dichroiccircular polarization layer 13, so that a condition with very goodcontrast is achieved.

A liquid-crystal display 130 according to the twelfth embodiment of thepresent invention, shown in FIG. 27, is described below. Thisliquid-crystal display 130 includes the light source 12, the linearpolarization separation layer 32, a liquid-crystal layer 134 having aretardation value that shifts the phase of transmitted lightsubstantially by π (refer to FIG. 28), and pixel electrodes 134A and134B that apply an electrical field to this liquid-crystal layer 134.The liquid-crystal display 130 further has a liquid-crystal cell 132whereby incident linearly polarized light that passes through a linearpolarization separation layer 14 and the auxiliary dichroic linearpolarization layer 15 is converted before it exits from the otherdirection with respect to the linear polarization separation layer 32 toanother linearly polarized light of a direction that is perpendicular tothe above-noted linearly polarized light, by a change in the directionof the directors in the liquid crystal by application of an electricalfield to the liquid-crystal layer 134 from the pixel electrodes 134A and134B, and the light-absorption type dichroic linear polarization layer18 disposed on the side of the liquid-crystal cell 132 opposite of thelinear polarization separation layer 32, and which receives linearlypolarized light that passes through the liquid-crystal cell 132.

Because the liquid-crystal cell 132, with the exception of theliquid-crystal layer 134, is same as the liquid-crystal cell 16 show inFIG. 4 to FIG. 6, other parts will not be described herein.

The liquid-crystal layer 134 is adjusted so as to have a retardationvalue that shifts the phase of transmitted light by substantially π,regardless of whether or not an electrical field is applied to the pixelelectrodes 134A and 134B, the retardation value being substantially thesame. This adjustment can be done by a known liquid crystal (forexample, a nematic liquid crystal) by control of the birefringence andthickness of the liquid-crystal layer. The direction of the directors Dis substantially parallel with respect to both the of the substrates 20Aand 20B.

The above-noted expressions “(shifted) substantially π/2” and“substantially parallel to the substrates 20A and 20B” include the casesin which there is a slight shift from the ideal condition, because of apre-tilt in the liquid crystal or various external disturbances.

If the above-noted shift is described in terms of the Poincare sphere ofFIG. 2, for example, if horizontal linearly polarized light representedby a point H on the equator is shifted with a direction angle of λ=0 inthe positive direction, it reaches to the point V on the equator of thePoincare sphere. That is, the horizontal linearly polarized light isshift by π so that it becomes vertical linearly polarized light.

As noted above, when the phase of horizontal linearly polarized light isshifted by π, this becomes vertical linearly polarized light that isperpendicular to the horizontal linearly polarized light. Therefore, iflinearly polarized light is caused to be incident at an angle of 45°with respect to the director direction of a liquid crystal having aretardation value that shifts the phase of light by π, the linearlypolarized light that is perpendicular to the above-noted linearlypolarized light results.

If the director direction within the liquid crystal is rotated with theplane without a change in the retardation value of the liquid crystal,the polarization condition changes from the condition of the onelinearly polarized light to the other linearly polarized light having adirection perpendicular thereto. For example, if linearly polarizedlight is caused to be incident at an angle of 0° with respect to thedirection of the liquid crystal, the polarization condition of thelinearly polarized light ideally does not change, and if the linearlypolarized light is caused to be incident at an angle of 0 to 45° withrespect to the direction of the liquid crystal, the polarizationcondition of the linearly polarized light is an arbitrary condition upuntil linearly polarized light that is perpendicular to the above-notedlinearly polarized light. The linearly polarized light is moved to anarbitrary point on the equator of the Poincare sphere of FIG. 2. Thatis, it is possible to change the direction of the electrical fieldvector of linearly polarized light incident to the liquid-crystal layersubstantially in the range from 0 to 90°.

In a liquid-crystal display 130 as described above, of unpolarized lightexiting from the light source 12 linearly polarized light of aparticular direction, for example, a horizontal linearly polarized lightis transmitted, with a component perpendicular thereto being reflected.

Because the reflected linearly polarized light component is reflected bythe reflective layer 12A of the light source 12, in the case of ascattering sheet, for example, 50% of the light becomes horizontallinearly polarized light, which is transmitted through the linearpolarization separation layer 32. This is true even in the case in whichthe light scattering sheet exists in the light path.

The linearly polarized light that has passed through the linearpolarization separation layer 32 strikes the liquid-crystal cell 132, atwhich depending upon the direction of the directors of theliquid-crystal layer, the direction of the electrical field vector issubstantially changed from 0 to 90°.

More specifically, according to the retardation in the liquid-crystallayer 134 of the liquid-crystal cell 132, the horizontal linearlypolarized light becomes vertical linearly polarized light, and byapplying a voltage to the liquid-crystal layer 22 from the pixelelectrodes 134A and 134B, the director direction is changed withoutchanging the retardation from substantially π, thereby changing thedirection of the electrical field oscillation vector of the linearlypolarized light passing through the liquid-crystal cell 132 by theaction of the applied electrical field by substantially 0 to 90°.

In particular, it is preferable that a circuit 26 (referring to FIG. 4)be provided that controls the voltage between the electrodes so that thedirector direction of the liquid crystal is substantially changed by 0to 45°.

If this is done, as described above, the phase of linearly polarizedlight incident to the liquid-crystal cell 132 exits from theliquid-crystal cell 132 in a polarization condition changed up tolinearly polarized light perpendicular to the polarization of theincident light.

If the polarization transmission axis of the dichroic linearpolarization layer 18 is caused to coincide with one of the twopolarization directions, by controlling the electrical field applied tothe liquid-crystal layer 134 so that the direction of the directors ofthe liquid crystal are changed substantially by 0 to 45°, it ispossible, similar to the case of the liquid-crystal cell 16 of FIG. 4,to adjust the amount of light passing through the dichroic linearpolarization layer 18 from the minimum to the maximum amount, therebyenabling achievement of a good display function, such as a gray-scaledisplay function.

FIG. 27 shows the so-called light display condition of linearlypolarized light exiting from the dichroic linear polarization layer 18and, as shown in FIG. 29, but if the direction of the directors D of theliquid crystal in the liquid-crystal cell 132 is changed so that thepolarization direction of linearly polarized light exiting from theliquid-crystal cell 132 is perpendicular to the case of FIG. 27, theso-called dark display condition will results.

Because the dichroic linear polarization layer 18 is made of alight-absorption type dichroic polarizer, even if external (unpolarized)light strikes the surface of the dichroic linear polarization layer 18,50% thereof is absorbed, and the remaining 50% is transmitted, so thatthere is almost no reflected component, therefore enabling a greatsuppression of a reduction in screen contrast in the liquid-crystaldisplay 130.

In this liquid-crystal display 130 as well, it is possible to disposethe auxiliary linear polarization layer 15 between the linearpolarization separation layer 32 and the liquid-crystal cell 132.

In this case, linearly polarized light that has passed through thelinear polarization separation layer 32 is transmitted through theauxiliary dichroic linear polarization layer 15, while the remaininglinearly polarized light that is not reflected by the linearpolarization separation layer 32 is absorbed. Therefore, a condition isachieved in which there is excellent contrast.

A liquid-crystal display 140 according to the thirteenth embodiment ofthe present invention, shown in FIG. 30, is described below.

In FIG. 30, elements corresponding to those in the liquid-crystaldisplay 130 of FIG. 27 are assigned the same reference numerals, and arenot explicitly described herein.

The liquid-crystal display 140 shown in FIG. 30 is the liquid-crystaldisplay 130 except that it is a reflective type, in which thelight-absorbing layer 36 is provided in place of the light source 12 ofFIG. 27.

Because other aspects and elements of the configuration are the same asthe liquid-crystal display 130 shown in FIG. 27, corresponding elementshave been assigned the same reference numerals, and are not explicitlydescribed herein.

In the reflective type liquid-crystal display 120, external(unpolarized) light strikes the dichroic linear polarization layer 18,at which only horizontal linearly polarized light coinciding with theestablished transmission axis thereof is allowed to strike theliquid-crystal cell 132. The other linearly polarized light component ofthe external light is absorbed by the dichroic linear polarization layer18, so that reflected light is not allowed to reduce the screencontrast.

The direction of the electrical field oscillation vector of horizontallinearly polarized light striking the liquid-crystal cell 132 issubstantially shifted by 0 to 90°, by the existence of theliquid-crystal layer 134.

While the retardation value of the liquid crystal in the liquid-crystalcell 132 tends to cause the horizontal linearly polarized light tends toshift so as to become vertical linearly polarized light, by applying avoltage to the liquid-crystal layer 134 from the pixel electrodes 134Aand 134B, the directors rotate within the plane, without a change of theliquid crystal retardation value from a, the result being that, inaccordance with the angle formed between the direction of the electricalfield vector of the linearly polarized light and the phase-lag axis orphase-lead axis of the liquid-crystal layer, there is a change from thelinearly polarized light to some arbitrary linearly polarized lightcondition, up to the condition of linearly polarized light perpendicularto the original linearly polarized light.

Therefore, linearly polarized light exiting from the liquid-crystal cell132, depending upon the direction of this polarization axis, isreflected at the linear polarization separation layer 32, the remainingcomponent being transmitted through the linear polarization separationlayer 32. Linearly polarized light reflected from the linearpolarization separation layer 14 is returned to the liquid-crystal cell132 and exits from the dichroic linear polarization layer 18 as displaylight.

The amount of light reflected from the linearly polarized light linearpolarization separation layer 32 and passing through the liquid-crystalcell 132 can be adjusted by a voltage applied to the liquid-crystallayer 34. By doing this, it is possible to obtain a gray-scale display.

Polarized light having passed through the linear polarization separationlayer 32 is absorbed by the black light-absorbing layer 36, therebyremoving this light, so that there is excellent contrast compared to thepolarized light (display light) reflected from the linear polarizationseparation layer 3 and passing through the liquid-crystal cell 132.

In the liquid-crystal display 140 as well, it is possible to dispose theauxiliary dichroic linear polarization layer 15 between the linearpolarization separation layer 32 and the liquid-crystal cell 132.

In this case, part of the linearly polarized light exiting from theliquid-crystal cell 132 is transmitted through the auxiliary dichroiclinear polarization layer 15, the remaining light being absorbed by theauxiliary linear polarization layer 15. Therefore, it is possible toachieve a condition with excellent contrast.

The liquid-crystal display 10 shown in FIG. 1 is formed by lamination ofa circular polarization separation layer 14 formed by a planar orientedcholesteric liquid-crystal layer, a liquid-crystal cell 16 having aretardation value so as to shift the phase of light by substantiallyπ/2, and a light-absorption type dichroic linear polarization layer 18.

By applying an electrical field to the liquid-crystal cell 16 andchanging the directors of the liquid-crystal layer 22 while holding theretardation value of the liquid crystal constant, it was possible toimprove the efficiency of light utilization, without a great reductionin contrast caused by external light.

The liquid-crystal display 30 shown in FIG. 8 was made by lamination ofa linear polarization separation layer 32 made of an extended multilayerstructure, a liquid-crystal cell having a retardation value so as toshift the phase of light substantially by π/2, and a dichroic circularpolarization layer 34 made of a light-absorption type dichroic linearpolarization layer with a λ/4 phase-shifting layer, this resulting in animprovement in the efficiency of light utilization, without a greatreduction in contrast caused by external light.

The reflective type liquid-crystal display 40 shown in FIG. 10 wasformed by laminating a cholesteric liquid-crystal layer as a circularpolarization separation layer 14, a black light-absorbing layer 36, aliquid-crystal cell having a retardation value so as to shift the phaseof light substantially by π/2, and a light-absorption type dichroiclinear polarization layer 18. In this case as well, there was no greatreduction in contrast caused by external light. A polarized lightcomponent transmitted through the liquid-crystal cell that is notcompleted changed to circularly polarized light is absorbed by theauxiliary dichroic linear polarization layer 13 and blacklight-absorbing layer 36, thereby removing this light, so that a displaycondition is achieved having excellent contrast.

In the reflective type liquid-crystal display 50 shown in FIG. 12, theeffect achieved is the same, and it was possible to achieve a darkdisplay condition with excellent contrast.

The liquid-crystal display 60 shown in FIG. 14 was fabricated bylaminating a cholesteric liquid-crystal layer as the circularpolarization separation layer 14, a liquid-crystal cell 62 having aretardation value varied by an applied voltage so that the phase oflight is substantially shifted by 0 to n, and a light-absorption typedichroic linear polarization layer with a λ/4 phase-shifting layer asthe dichroic circular polarization layer 34.

With an electrical field applied to the liquid-crystal cell 62, so as tovary the retardation value of the liquid crystal, it was possible toimprove the efficiency of light utilization, without a great reductionin contrast caused by external light.

The liquid-crystal display 70 shown in FIG. 17 was fabricated bylamination of an extended multilayer structure as the linearpolarization separation layer 32, a liquid-crystal cell 62 similar tothat noted above, and a light-absorption type dichroic linearpolarization layer 18, and, similar to the above-noted case, it waspossible to improve the efficiency of light utilization, without a greatreduction in contrast caused by external light.

The reflective type liquid-crystal display 80 shown in FIG. 19 wasfabricated by lamination of a cholesteric liquid-crystal layer as thecircular polarization separation layer 14, a black light-absorbing layer36, a liquid-crystal cell 62 the same as noted above, and alight-absorption type dichroic circular polarization layer 34. In thiscase, there was no great reduction in contrast caused by external light.Additionally, the linearly polarized light component transmitted throughthe liquid-crystal cell was absorbed the black light-absorbing layer 36,and thereby removed, so that a display condition with excellent contrastwas achieved.

In the reflective type liquid-crystal display 90 shown in FIG. 20, theeffect achieved is the same, and it was possible to achieve a displaycondition with excellent contrast.

The liquid-crystal display 100 shown in FIG. 100 was fabricated bylamination of a cholesteric liquid-crystal layer as the circularpolarization separation layer 14, a liquid-crystal cell 102 having aretardation value varied by an applied voltage so that the phase oflight is substantially shifted by −π/2 to π/2, and a dichroic linearpolarization layer 18.

With an electrical field applied to the liquid-crystal cell 102, so asto vary the retardation value of the liquid crystal, it was possible toimprove the efficiency of light utilization, without a great reductionin contrast caused by external light. In the reflective typeliquid-crystal display 120 shown in FIG. 26, the effect achieved is thesame to the above-described.

The liquid-crystal display 110 shown in FIG. 24 was fabricated bylamination of an extended multilayer structure as the linearpolarization separation layer 32, a liquid-crystal cell 102 similar tothat noted above, and a light-absorption type dichroic linearpolarization layer 34, and, similar to the above-noted case, it waspossible to improve the efficiency of light utilization, without a greatreduction in contrast caused by external light.

The liquid-crystal display 130 shown in FIG. 27 was fabricated bylamination of an extended multilayer structure as the linearpolarization separation layer 32, a liquid-crystal cell 132 having aretardation value varied by an applied voltage so that the director ofthe liquid crystal is varied, thereby changing the direction of theelectrical field oscillation vector of incident linearly polarizedlight, and a dichroic linear polarization layer 18.

With an electrical field applied to the liquid-crystal cell 132, so thatthe directors of the liquid crystal change, it was possible to improvethe efficiency of light utilization, without a great reduction incontrast because of external light.

The reflective type liquid-crystal display 140 shown in FIG. 30 wasfabricated by lamination of an extended multilayer structure as thelinear polarization separation layer 32, a black light-absorbing layer36, a liquid-crystal cell 132 similar to that noted above, an auxiliarydichroic linear polarization layer 15, and a light-absorption typedichroic linear polarization layer 18.

In this case as well, there was no great reduction in the contrastbecause of external light. Additionally, a polarized light componentpassing through the liquid crystal is absorbed by the blacklight-absorbing layer 36, being thereby removed, so that a displaycondition with excellent contrast is achieved.

INDUSTRIAL APPLICABILITY

A liquid-crystal display according to the present invention achieves agreat improvement in the efficiency of light utilization, and, by makinguse of the birefringence of a liquid-crystal layer, enables theachievement of a display condition with excellent contrast, without agreat reduction in contrast caused by external light.

1. A liquid-crystal display comprising: a dichroic polarizing layerhaving one of a function whereby of the incident light, a lightcomponent having circular polarization of one direction, either right orleft, is transmitted, and a component of another circular polarizationdirection is absorbed, and a function whereby one linearly polarizedlight component is transmitted and a linearly polarized light componentperpendicular thereto is absorbed; a liquid-crystal cell including aliquid crystal layer that shifts the phase of light passing therethroughand electrodes for applying an electrical field to said liquid-crystallayer, whereby one of circularly polarized light and linearly polarizedlight incident after being transmitted through said dichroic polarizinglayer is converted to the other before it exits the other side or is notconverted but the liquid-crystal cell also has one function of afunction that changes the ellipticity of the light if exiting ascircularly polarized light or changes the direction of polarization ofthe light if it is exiting as linearly polarized light; and apolarization separation layer having one of a function of transmitting alight component having circular polarization of one direction, eitherright or left, and reflecting a component of the other circularpolarization direction, and a function of transmitting one linearlypolarized light component and reflecting another component having apolarization direction perpendicular thereto, these being disposed inthis sequence as seen from the observation side, wherein light is causedto be incident from either said dichroic polarizing layer or saidpolarization separation layer side.
 2. A liquid-crystal displayaccording to claim 1, wherein said dichroic polarizing layer is adichroic circular polarizing layer which, of incident light transmits acircularly polarized light component of one direction, either right orleft, and absorbs a circularly polarized light component of the otherdirection, said liquid-crystal layer having a retardation value thatcauses a phase shift in the transmitted light that is substantially π/2,said liquid-crystal cell converting the incident circularly polarizedlight to linearly polarized light before it exits from the oppositeside, by applying an electrical field from said electrodes to saidliquid-crystal layer so as to change the orientation of the directorsthereof, thereby causing a change in the polarization axis of thelinearly polarized light, said polarization separation layer being madea linear polarization separation layer that, of the incident lightthereto, transmitting a light component of one linear polarization andreflecting another linearly polarized light component havingpolarization perpendicular thereto.
 3. A liquid-crystal displayaccording to claim 2, further comprising a circuit for control of avoltage between said electrodes, so that the direction of the directorsof said liquid crystal in said liquid-crystal cell is changed bysubstantially −45 to +45 degrees with respect to an electrical vectordirection of the incident linearly polarized light.
 4. A liquid-crystaldisplay according to claim 1, wherein the dichroic polarizing layer is adichroic circular polarizing layer which, of incident light transmitsone circularly polarized light component and absorbs another circularlypolarized light component, said liquid-crystal cell having the effect ofshifting a linealy polarized light phase of incident light substantiallyby −π/2 to +π/2, when said electrical field is applied to saidliquid-crystal layer from said electrodes so as to change theretardation value thereof, and the polarization separation layer being alinear polarization separation layer that, of the incident lightthereto, transmits a light component of one linear polarization andreflects another linearly polarized light component having polarizationperpendicular thereto.
 5. A liquid-crystal display according to claim 1,wherein said dichroic polarizing layer is a dichroic linear polarizinglayer which, of incident light transmits one linearly polarized lightcomponent and absorbs a linearly polarized light component perpendicularthereto, said liquid-crystal layer having a retardation value thatcauses a phase shift in transmitted light of substantially π/2, saidliquid-crystal cell converting incident linearly polarized light tocircularly polarized light before it exits from the opposite side, thedirector direction of said liquid crystal being changed by applying saidelectrical field to said liquid crystal from said electrodes, therebychanging the ellipticity of the circularly polarized light, and saidpolarization separation layer being made a circular polarizationseparation layer that, of the incident light thereto, transmits a lightcomponent of one circular polarization, either right or left, andreflects another circularly polarized light component having theopposite polarization.
 6. A liquid-crystal display according to claim 6,further comprising a circuit for control of a voltage between saidelectrodes, so that the direction of the directors of said liquidcrystal in said liquid-crystal cell is changed by substantially −45 to+45 degrees with respect to the light transmission axis of said dichroiclinear polarizing layer.
 7. A liquid-crystal display according to claim1, wherein said dichroic polarizing layer is a dichroic linearpolarizing layer which, of incident light transmits one linearlypolarized light component and absorbs a linearly polarized lightcomponent perpendicular thereto, said liquid-crystal cell being suchthat, with said electrical field applied to said liquid crystal layerfrom said electrodes, the retardation value of said liquid crystal ischange so as to shift the phase of the incident linearly polarized lightsubstantially from 0 to π, and said polarization separation layer beinga linear polarization separation layer that, of the incident lightthereto, transmits a light component of one linear polarization andreflects another linearly polarized light component having polarizationperpendicular thereto.
 8. A liquid-crystal display according to claim 1,wherein said dichroic polarizing layer is a dichroic linear polarizinglayer which, of incident light transmits one linearly polarized lightcomponent and absorbs a linearly polarized light component perpendicularthereto, said liquid-crystal cell being such that, with said electricalfield applied to said liquid-crystal layer from said electrodes, theretardation value of said liquid crystal is changed so as to shift thephase of the incident light substantially −π/2 to +π/2, and saidpolarization separation layer being a circular polarization separationlayer transmitting one circularly polarized light component of theincident light and reflecting the other circularly polarized lightcomponent of the incident light.
 9. A liquid-crystal display accordingto claim 9, wherein said dichroic polarizing layer is a dichroic linearpolarizing layer which, of incident light transmits one linearlypolarized light component and absorbs a linearly polarized lightcomponent perpendicular thereto, said liquid-crystal cell including aliquid-crystal layer having a retardation value that shifts the phase oftransmitted light substantially π, and applying the electrical field tothe liquid-crystal layer from said electrodes so as to change theorientation of the directors thereof, thereby causing a change in thepolarization axis of the linearly polarized light to the oppositedirection which perpendicular to the original light, and saidpolarization separation layer being made a linear polarizationseparation layer that, of the linearly polarized light incident thereto,transmits a light component of one linear polarization and reflectsanother linearly polarized light component having polarizationperpendicular thereto.
 10. A liquid-crystal display according to claim11, further comprising a circuit for control of a voltage between saidelectrodes, so that the direction of the directors of said liquidcrystal in said liquid-crystal cell is changed by substantially 0 to +45degrees.
 11. A liquid-crystal display according to claim 2, wherein saidliquid crystal layer of the liquid crystal cell is held between twosubstrates, the electrodes being formed on one substrate, wherein when avoltage is applied to said electrodes, the resulting electrical field asa part that is substantially parallel to said substrate surface, thedirection of the most of the liquid crystal molecules within saidliquid-crystal layer being in a mode in which they remain substantiallyparallel to said substrate surface.
 12. A liquid-crystal displayaccording to claim 2, wherein said linear polarization separation layeris a planar multilayer structure of three or more films havingbirefringence, wherein of two lights having oscillation directionsmutually perpendicular within the plane of each layer, the difference inindex of refraction between layers adjacent in the thickness directionwith respect to the other light.
 13. A liquid-crystal display accordingto claim 2, wherein said linear polarization separation layer is made upof a phase-shifting layer having a retardation value that shifts thephase of transmitted light by substantially π/2, and arotation-selective layer made of a cholesteric liquid-crystal layer,wherein circularly polarized light transmitted through or reflected bysaid cholesteric layer is converted to linearly polarized light.
 14. Aliquid-crystal display according to claim 2, further comprising anauxiliary dichroic linear polarizing layer between said liquid-crystalcell and said linear polarization separation layer, whereby, of theincident light, one linearly polarized light component is transmitted,and another linearly polarized light component perpendicular thereto isabsorbed.
 15. A liquid-crystal display according to claim 1, comprisinga light source disposed on the side of said polarization separationlayer opposite from said liquid-crystal cell, light from said lightsource passing through said polarization separation layer and strikingsaid liquid-crystal cell.
 16. A liquid-crystal display according toclaim 1 further comprising a light-absorbing layer disposed on the sideof said polarization separation layer opposite from said liquid-crystalcell, whereby light having passed through said polarization separationlayer is absorbed.
 17. A liquid-crystal display comprising: a dichroiccircular polarizing layer which, of incident light transmits acircularly polarized light component of one direction, either right orleft, and absorbs a circularly polarized light component of the otherdirections; and a liquid crystal cell, including a liquid crystal layerthat shifts the phase of light passing therethrough, and electrodes forapplying an electric field to said liquid crystal layer, these beingdisposed in this sequence as seen from the observation side, whereinsaid liquid-crystal cell having the effect of shifting a circularlypolarized light phase of incident light substantially by 0 to π, whereinsaid electrical field is applied to said liquid-crystal layer from saidelectrodes so as to change a retardation value thereof.